I assume your asking for quaratine time? I've read anywhere from 2 weeks to 2 months, mainly the latter type number for all the hyper-careful discus keepers out there, frankly I dont quarantine, which most people say is bad, and I'd possibly agree to some amount, on the other hand I've only ever had the occasional case of ich in my tanks (which are quickly killed off by raising the temp which does more damage to my plants than the fish) other than that I've had fin rot but that was on a group of betta that was given to us because of that fact (ie the were unsellable)
Basically what I'm saying is, if your confident in your supplier and the state of the fish then you might decide to skip quarantine though most people on these boards would disagree with me, and I bet even some of those skip it at times. Quarantine is simply up to an individual though I would reccomend for fresh wild caught fish for obvious, you may also want to use it for shipped fish though I can see the benifits adding shipped fish to a nice homely well cycled/conditioned tank compared the the sparse small not the best cycled that many quarantine tanks tend to be.
in the end only you can consider wether to quarantine and if so for how long. Do some research, see what things may carry and if any of your fish may easily catch or suffer from these possible items or on how long to quarantine and decide from there