Use of Perception to actively Search, you can take as many Move Actions as yo want without penalty of failure on that Skill check to look for traps/secret doors/etc...
Setting the DC in an OOC comment just determines the threshold for continued rolling, rather than spend 2 minutes IC time on the Take 20 for every square since when the player does not feel such scrutiny was necessary.
Ex: Searching, Perception(+7) against DC22
This is almost an like taking a 15, which would average 4 Move Actions to accomplish, so 12 seconds. So, the DM can use his real dice if necessary, or not roll anything if there are no traps or hidden things to be found.
I have found this technique really speeds up things in the PbP environment (except when the DM rolls everything with on-line dice rollers that is
) when rogue/scouts need to be wary of traps and such when the players do not want to or cannot afford to take 20's. Sure the DM does some rolling when there is something actually there, but he only needs to if the DC is higher than what the players threshold is at.