If PCs treat an old-school dungeon with any rational amount of caution, they will search every ten feet of floor for traps, listen at every door, and search every wall for secret doors. In other words, they’ll spam their at-will search abilities.
It’s a problem that Gary Gygax railed against in 1e:
Continual listening becomes a great bother to the
DM. While ear seekers will tend to discourage some, most players will
insist on having their characters listen at doors at every pretense.
4e has a general solution for spammed actions: make them encounter powers.
You could just make searching a regular encounter power, so it can only be done every five minutes, but I think it would be more interesting to make searches into a daily resource to be managed, like Fate points from Spirit of the Century-type games. During the day, you can search carefully for traps. Every time you search, and find nothing, you expend one of your searches. If you search and find something, you don’t expend a search. Furthermore, every time you blunder into a trap, you gain a use of your search power.
It makes sense narratively. If you’ve searched 100 consecutive doors for traps and found nothing, no matter how hard you try, you’re going to relax your vigilance. On the other hand, if you’ve been finding tons of traps, or if you see something about this door that makes you suspicious, you’re going to be far more alert.
We’ll leave all the search rules the way they are: we’ll just add to them. At the beginning of every day, every character gets a number of Search tokens equal to their Perception bonus. Rogues get, say, three extra tokens.
Whenever a PC wants, they can risk a Search token to get a +5 bonus to a Perception check. If the check doesn’t turn up anything interesting, they lose the token. If they find a trap, treasure, a secret door, or anything else hidden, they get to keep their token. Every time a PC falls victim to a trap, they get a Search token BACK. This represents their suddenly-increased attention level.
This system would reward players for searching judiciously, based on clues and intuition, not as part of a mindless sweep.
To compensate the PCs for their extra search power, every Perception DC in the game is 5 points harder.
I think this would encourage people to play the way that Gary wanted them to play: to search for traps and listen for monsters judiciously, when they have a reason to be suspicious – and to blunder blindly into the occasional ambush for the DM’s amusement.