To keep it brief, dh's interests have him out of the house for a couple of hours at the weekend (effectively taking out a morning), and at least one evening every week. Sometimes additional times, and it can be for longer.
The rationalization has always been that he would look after DC if I wanted to do something, so I can't complain. The reality is that my interest is more home based, so I'm still regularly disturbed by DC, cutting into my time and breaking concentration. It's not something I can just pick up and take elsewhere. Also wouldn't be doing it all through the school day due to other commitments.
AIBU to tell him to entertain his DC (quietly) for the relevant length of time so that I have my undisturbed hobby time too?