On an AT with worn out clutches, dirty fluid can sometimes keep it going a little longer due to the abrasive particles suspended in the ATF creating friction on the worn out plates. But, total failure will happen very soon anyways.I did 2 drain and fill, a little bit afraid to do the third as some say losing too much 'stuff' in there might cause the tranny to slip. Then of course 4-5 years later this happens. I imaging it leaked about 3.5 QT and I put back in a little bit more than 4QT with the cooler installed. Going to do another D+F when I have the chance before winter settles....
So you did 2 drain and fills 5 yrs ago, is that correct? None since?
But, you have been replacing the ATF due to leakage so at least you are adding some new fluid with fresh additives which do help clean.
1) Do at least 3 drain and fills with a compatible ATF such as DW-1, Amsoil, Valvoline MaxLife Dex Merc ATF, etc
2) Find the leak as the AT should not be using fluid.
3) One pint overfill is not going to hurt that AT (I think that is around 3/8" over the full mark)
4) Being between the Full and Add mark is what is recommended by the mfg, but IMHO, being at the Full mark or slightly above is better: more fluid for cooling and extra in case of a leak.
I am NOT an AT expert, just advising on what I have heard and learned in this and other forums.