I've mostly never bothered with adjusting airsoft optics tbh. The target is either close enough that I just use instinctive aiming, or it's far enough that an airsoft gun can't print any sort of useful group at said range in order to zero. A very coarse adjustment to get the wide area of spray at 50m+ roughly kinda midde-ish within the actual glass window (optic type dependant) is all I bother with and you can often do that just pre game while making any necessary hop adjustment for the bbs you've got that day. Then once in game you simply put the baddie in the middle of the glass, spray, and pray.
When I have zero'd a RIF it was at around 10m, 15 max, as I only have the TM bb catcher that's got a target area roughly 9-10" square. The one time I used it to zero (was shooting a KWA GBB) I had to be very much sub 15m in order to shoot groups that were actually small enough to clearly define a mean point of impact and then be able to make any sort of useful sight adjustment.
