When I met my present and most fulfilling Sub, we ageed before hand on our "rules". One of them was no penetration. This rule has since been changed, but the point is. Any and all is talked about. Some D/s relationships involve no sex and others involve " full " sex as you put it.
A master must have time and be honest and open with his submissive. The submissive must do the same. Honestly and being open is paramount, the time is not, necessarily. Some relationships are strong and secure with very little time together. As long as you secure the feelings someway else, email, voice, contact with them. Nobody faults anyone for being honest.
My thoughts anyway..hope it helps you dear.