We always talk about this as if the only opportunity to communicate the sub's desires is during the scene.

Fascetiouly, I'm asking... don't any of you talk about bdsm/kink/ 'D/s' any other times?

The point being that topping from the bottom is an in-scene event, discussing gratification and desires, needs and fantasies of both Dom and sub can occur virtually any other time without it being considered topping.

And as far as in-scene conversation is concerned, some of us dominants, are quite adept at coercing their subs into revealing both their darkest and their immediate needs during the scene. My girl doesn't need to top, doesn't get a chance to top, because I'm topping her mentally too, making her give herself to me body and mind, "forcing" her to follow me exactly to where she wants to go... (if that makes sense... lol )