Then can you explain the context better? The PCs have identified an obstacle, as DM you're telling them what is required to overcome that obstacle and how long it will take. In the case you mentioned it was a trap, I've given examples of a lock.
Sure! I agree, a lock is probably a better example to use, as it has fewer moving parts, so it cuts to the real issue more directly.
I think the lock example is a little simpler if that's okay as a start. I don't want to get into specific verbiage of how skills are involved, that's pretty secondary. So a slightly abbreviated encounter might look something like ..
I actually think the specific verbiage of how skills are used is very relevant. I think a lot of our misunderstandings are coming from assuming that these sorts of specifics don’t make much difference, when in reality they make all the difference. But, I will try to engage in the example as you present it.
DM: The door has a padlock on it.
Joe: I take a closer look, is it trapped?
DM: Make an investigation check
Joe: 15
DM: As far as you can tell there are no traps, do you you attempt to open it? [DM knows it's a DC 20]
Joe: Yep, I get a 17.
DM: It's apparently more difficult than it looks It doesn't open, you can keep at it but if it doesn't open right away it could take a few minutes, even up to half an hour.
Joe: Okay, I'll try again for a few minutes.
DM: [Rolls in secret, gets a low number meaning it's going to take a while.] You've tried for about 5 minutes, how much longer do you want to try?
Joe: Ugh, tough lock. We haven't seen a patrol yet [there is no immediate time concern, but some] so I'll try up to half an hour.
So I never told the PC exact numbers, just generalities. I might have variations on this but that's the gist. There may even be situations where the 15 investigation wasn't high enough to find an alarm trap and the padlock can't be opened even after half an hour (in world time, not game time) in which case either guards will have shown up or I'd say something about the lock being broken.
This looks a lot like the way I’ve seen other DMs run such situations, and if you enjoy that, awesome. I’ll try to follow along with the same scenario, but more how it would look if I were DMing. An important thing to keep in mind is that I use periodic checks for complications (which can include wandering monsters, but also other things that make the PCs’ lives more complicated) to apply time pressure. A
lot of player decisions come down to managing time. I use different time scales for different contexts, but basically a time-consuming action eats up about a sixth of the interval between checks for complications, and a dangerous action can trigger a check for complications early. Some actions are both time-consuming and dangerous, some are one or the other, some are neither. With that out of the way, here’s how that scene might go at my table:
DM: The door has a padlock on it.
Joe: I take a closer look. Is it trapped?
DM: I am hearing your goal is to find out if it’s trapped, could you be a bit more specific about how you try to find that out?
Joe: I don’t want to touch it or anything, I’m just giving it a thorough visual inspection.
DM: You don’t see anything out of the ordinary for a padlock of this make.
Joe: Ok. I want to try to pick it.
DM: Alright, it’s going to require DC 20 Dexterity check to open, and I’ll add a die to the time pool.
Joe: Hmm… Alright, but I want to spend inspiration to get advantage on the check.
DM: Sounds good. Alice, what are you doing during that time?
[I’d go around the table getting everyone’s action declarations before proceeding to resolution, then…]
DM: Ok, how’d you do on that lock, Joe,
Joe: Only a 17, so I haven’t got it open yet.
I’d then proceed with resolving the other players’ actions, re-establish the scene accounting for what changed as a result of those actions, and ask what the players what they want to do. If Joe wants to keep trying for a half hour, that would be two repetitions of this cycle, but one of the advantages of this method is that he doesn’t have to commit to the full half-hour. After each attempt he can re-assess the situation and decide to keep going or try something else instead. As time advances towards the next complication roll, this may affect the players’ priorities and strategies, just as it would the characters’.
FYI: I have a game and won't get back to this for a while.
Awesome, I hope it goes well!