If a mature Doe or yearling fails to get breed during the "1st or 2nd" rut, do they return into estrous 28 days(or whatever the cycle is) later, and keep doing so until she is breed?

In all the information that I have read, that is the case. If they are mature enough to come into estrus, they will continue to do so until they are bred. This is the reason some fawns with spots are seen well into the fall. Offspring of late bred does.

I guess what I am trying to ask is, at what point does a Doe stop having a estrous cycle if not bred? Does it stop when the days start getting longer?