Has anyone requested their past LESs from DFAS? How long did it take?

I have no *good* answer to your question. But I have a caveat. Please remember that we are not in a time of "normal." Asking how long something "usually" takes *may* be irrelevant in the time of COVID. I understand your frustration, and I also understand this answer will likely not serve to assuage said frustration. But almost anything administrative takes longer these days.

You should already be able to pull down your previous LES's in MYPAY. If you don't have access or need additional information I would recommend contacting them directly.
https://www.dfas.mil/civilianemployees/understandingyourcivilianpay/LES/