I'm sure some of you might be saying that while on vacation you could have something happen or uncover some clue to what the heroes might have been looking for, but that's not a vacation that's an adventure with a vacation theme. A key point is this is a player asking about having time off, not thinking they get time off to just have it turn into a job. With that said I do, however, want to make it very clear I'm actually all for down time, just not how that one player asks for it.
I use the above as an example of what I feel a lot of GMs worry down time will become and what a lot of players seem to think they want down time to be, a grinding halt to the life or death heroics for a while. Instead I'm going to try and cover some of the broad issues I've seen people have with down time then talk about how I've come to interpret it.
The Ticking Clock
I've seen posts about how allowing down time removes the tension and urgency from a game. Sure if the villain is trying to open a gate to hell and in three days he might just succeed then yes stopping for a beer is a bad idea, but is every one of your adventures on a clock and what about right after they stop the threat is there another waiting in the wings to kick up the second this one is resolved? I'm not against putting heroes up against a deadline to motivate then, but this shouldn't be the norm. If everything is about rushing to save the world then how do you know when the really big bad threats come along? When it comes to this attitude I remind myself of the saying "If everyone's special, then no one is." This is just as true here. Save those countdowns for the big parts of your story where the heroes thought they had all the time in the world and now they need to make a mad dash to save everything. Giving time for breathing room just accentuates the times when there's not.
Just Get to the Action
There's also games out there that just seem to see things that aren't combat as a side note to their games and not actually worth their time. For this I say, try war gaming. This isn't meant to be an insult, just if you have no interest in character development then look at a game that caters to that. A good old dungeon bash can also work here as while in a dungeon you can have all the combat you want, but even then think about letting your characters have fun and unwind when they get out. Give your players chances to hang out in town or while they're camping. Down time is a great way to let players add depth to characters and form bond so when that next combat comes they can slowly start to be fighting for more than just the XP and loot.
What About Balance
Ok here is one that I'll admit can make downtime a double edged sword, but it doesn't have to be. I've come across a GM or two that refuses to do downtime anymore because they used to and a player found a way to make that time completely screw up their plans. Sometimes it's a player milking a system so that they make more cash than they would adventuring, sometimes its making an item themselves that the GM planned on requiring a quest to obtain. Now this is actually a section that I could do an entire article on, but I'm going to make it simple for now. Down time does not mean players can do anything and it becomes a reality. Sure you can run down time like that, but you're then asking for problems. If a player finds a way to make more money in town than adventuring and all your player cares about is making money then you need to talk to them about if their character would go back to adventuring at all. There's other aspects to this like "sure you can make 200gp for of this a day, but that doens't mean people have the money to buy it all" or "well yea, but you're a new business and your competition has been running for 50 years, they're either going to know how to deal with an upstarts or people jsut aren't gong to leave the shop they know," but like I said I'm just handling the over arching problem of downtime getting out of hand. As for the wizard making an item you wanted them to quest for then don't let that item just be made by anyone with enough time, especially if it's one of those cases where someone else is after it too. When it comes to issues like this you need to make it clear that somethings just can't be done without the proper training, tools, supplies, or whatever that makes this action somehow break your game. On the flip side also need to note that if a player making 20 gold in a card game ruins your game then it might not be your players that are the problem .
What I Do:
The Episode Method
I come from a background a writing for TV and Movies so that's how I tend to see stories. I try to run most of my adventures like episodes with any deadlines being limited to either a session or two or so far out that it is expected that the heroes won't be rushing 24/7. That also means that there can be time between sessions/episodes sometimes, usually not more than a week or two, but still enough that one adventure doesn't just bleed into the next. Then for my really big or important adventures I just treat t like a two or three part episode. Those big moments when an hour (or session) just isn't enough and those ones end with "to be continued". This might sound hokey, but also think about how shows run. They usually have a big arch for the season (the villian's plan that stretches a campaign), episodes that sometimes directly effect that story (Main quests), some filler episodes (side quests), and a mid season and end season finales that are usually two parts episodes (those big adventures where the clock starts ticking and time really matters). Those filler episodes can even be the result of downtime activities like getting a drink or shopping for an item that leads a hero into a story that while it has nothing to do with the main plot is still there and up to them if they look into.
Make the Little Stuff Matter
Personally I try to put most of my down time at the beginning and end of adventures as to not interupt the flow once a story is off and running, but don't be afraid to look at them as hooks for plot. You have a wizard that wants to go shopping looking for magic items? Fine let him and have a merchant try to sell him one, the catch is maybe it's stolen or cursed or even isn't magic but holds a secret leading to an ancient treasure. These are all just more adventures in the waiting that down time can bring to your players rather than them looking for them. Your fighter or bard want to stop at an inn for once and just unwind? Make a contact NPC need to meet them at an inn and let your characters unwind while also getting the job done. If you feel like things that aren't part of some kind of quest isn't important than find ways to bring those activities into your adventures.
I feel like this article would have been much more useful a couple years ago as more and more games are looking at the time between adventures as being almost as important as the adventures themselves, I'm looking at you 5e, but I still hope this helps. I'm gong to leave you with one last tool I use for down time. Like I said I sometimes to campaigns where each session can be up to a couple week in game time after the last one ended. What I do to fill those gaps is something I kind of stole from Savage Worlds, but tweeked for my purpose. In SW there is a mechanic called "Interludes" where when the heroes are hanging out they can draw a card and use it to inspire them in a story they tell their friends about their past. I do love this as a way to flesh out characters while playing, but it wasn't quite what I was looking for. Rather than change any of the mechanics, I just changed how you use them. Whenever I start a game that has jumped some time my players get to draw a card and use it to tell me what their character was up to in that time. Here;s a Break down of what the cards mean:
Clubs: Something tragic happened to you
Spades: You had some kind of success or victory
Diamond: You have come across something or someone you now desire
Hearts: You have become entangled in some kind of love story
Joker: These are special basically tell me what you want to have happened and as long as it doesn't break the game I tend to allow it, usually granting some sort of perk to the character.