I think generally most experienced people will wait about 2 to 3 days at least, and a week if possible before putting into a case, box or bag. I did have a few that gassed up about two weeks after being made. BUT those were some that I made in Japan and then two weeks later put them in a bag inside my suitcase in which I brought back to the States. Two weeks and 16 hours of flight in a bag. That may have had something to do with it.
Still, to get a scientific time limit will be hard to do, in my opinion.
IF a pen is not going into a case, box or bag, it is usable within minutes to an hour. But I still let mine cure for a day before giving it to anyone.
I just re-read your post. I usually assemble almost immediately after finishing, but not always. To me, that (assembling) has less to do with fuming than enclosing the parts in an air tight space.