Certainly it is no problem to spend a short amount of time in a park if you have a season pass - you can come back anytime.
Shortest time as a normal (non-season) guest: 4 hours at Wild Adventures, Valdosta, GA - there isn't all that much there, and there never seem to be any lines. My husband doesn't work well with circular rides, so we pretty much do the coasters and leave.
Shortest time as an employee: Probably 10 minutes, going on the Corkscrew and back out, just for a kick. Or the 5 minutes it takes to cross from one set of dorms to the other, just walking across the midway - but that doesn't exactly count! :)
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Po!nt of View: A different look at Roller Coasters.
http://www.crosswinds.net/~justmayntz/thrills/index.html Let's get the POLL to 100 VOTES today!