That's a variant rule that you're houseruling, sure. But it's not RAW. Taking 20 on a search, to me, implies taking out a magnifying glass and getting on hands and knees, not walking around.takasi said:http://www.d20srd.org/srd/movement.htm#forcedMarch
You walk in the dungeon while searching, so I think this rule should apply. Rest isn't required after 8 hours but there are potential problems if you continue for "eight days straight".