I mean did Brett Favre ever explain why he kept retiring and coming back?

Freedom to change your mind, not in the US Constitution but it is a fundamental human right I guess.

I would assume that with the providers it is probably a result of getting into a relationship, perhaps with a client, or perhaps a non-client. Especially if it is with a client I would assume that the said client/new boyfriend-sugardaddy-whatever, would probably desire that he himself see that retirement announcement be made, perhaps just to be secure in his own mind.

Not sure how that works because I don't date or wish to date girls I see.

I doubt the reason that girls retire is not because they have amassed enough money to live on (and then run out as you speculated on), it is probably for the said reason or some other personal matter.

Also girls retiring for months is actually pretty significant compared to some "retirements" I have seen that have lasted 2 or 3 weeks.