Most of the time I have severed the layered branches from the mother tree after six weeks and all survived. In many cases the plant will show signs of shock and show drooping leaves or some leaves dropping but that is understandable. The plant will adjust its vegetation according to the roots (or how much the roots can sustain it). Gradually the leaves will show more life (and leaf buds may appear where leaves were lost). It is better to keep it away from hot sun for a couple of weeks.
I did airlayering earlier and separation took place in growing season and the air-layered plant showed some more growth.
If your air-layered plants start going into dormancy and the leaves start dropping, don't be discourage because the roots will still grow until very cold weather sets in (i.e. it will survive).