Time to find a Secret Door

[psydraco]

Hi friends!

Exploits p. 19 says

"Finding them always requires an active search; the GM rolls secretly against the highest of Vision, Observation, or Per-based Traps for each searcher. Success reveals a door, if there is one; it may require an IQ-based Traps roll to open. These rolls often have steep penalties.

How much time of a active search requires to find one? I know it can vary depending on how big is the room and any other variants. But for the porpouses of Wandering Monsters hourly rolling and to have a reason for the players not stop on every room to search for them, how much time would require, maximum and minimum, considering margin of succes and any other variant (ideas are wellcome).

Thanks!