When I was younger I could do about five sets of 25 pull-ups. I wish I still had that strength.
Now in my 40's I will do one set of ten pull-ups, then one set (with a light band) of ten pull-ups and then one set (with a medium band) of ten pull-ups. My understanding is that the set's muscle tension period should be at least 45 seconds to get anything productive. Isometrics and negatives also help to go beyond.
Keep pushing and going strong!
💪🏼😁