I personally would expect to have potential buyers inspect and perhaps test play a game or two in under 30 min. I mean, what really needs to be done? look at circuit boards for hacks, under playfield, upper playfield, cabinet art. Play. Buy or go home. These things aren't generally cheap and if someone is looking to drop 3 - 6k or whatever the case may be, it is fair to give them a bit of time to look at stuff.