I said 5 minutes, although that's because 30 seconds is too short. Realistically, it takes about a minute or so. I do almost all my gaming online now, so I have the SRD up and running. Gotta love hypertext SRD's that are searchable. I can generally find, read, copy and paste the rule into OpenRPG within a couple of minutes and that tends to end arguements.
By the same token, in my last campaign, I had a player who was a failed rules lawyer. I have no problems with people challenging me on rules, but, then again, when it turned out to be every ten minutes and me being right 99% of the time, something had to be done. So, to forestall further breakdown, I instituted the following house rule:
Any player could challenge a rule at any time. However, if the challenge is mistaken, then the player forfeits all xp for that session. If you're going to waste my and every one else's time, you better be bloody well sure that you know what you're talking about. Otherwise, leave it until after the session.
It worked for my group. I've never had any problems admitting when I don't know something, but having someone constantly challenge me on things that I did know became annoying.