Out of curiosity, what are the use cases for adding nodes after get_ready has already produced nodes?

I was wondering about avoiding the need to call prepare() by having it automatically do the cycle-checking at the first get_ready() call and then raising ValueError if add() is called any time thereafter.

Assuming we do want to be able to add() after a get_ready(), is there a reason that "forgetting" already-produced nodes is the correct behavior, as opposed to remembering all nodes ever added, and raising iff the addition creates a cycle among all nodes ever added or depends on an already-yielded node?