Seems to be a general rule to spend all available stamina before long AFK times (aka while sleeping, working, studying, etc), and I follow that rule myself too, but I'm aiming to those cases when stamina replenishment occurs at very different times between games, which is specially true when the player started to play each game at different dates (most likely case, IMO, I don't think too many people started playing 2 or 3 games the same day).
This also applies to those players who haven't reached the necessary stamina to fully cover long AFK times.

Anyways, having counter-measures to deal with shorter stamina replenishment times it's only useful when you have enough time to keep checking games up (i.e.: weekends, vacations, etc). So during normal busy days, looks like the safest approach is to stick to fully stamina usage before going AFK, and if stamina gets replenished before you can be on-line, then bad luck xD