Keeping fresh fluid and a unrestricted filter will add life to any transmission.
Change it very often and you might be shocked at the extended mileage you get.
Some failures are just going to take place due to design flaws.
With that said, the concern of changing the fluid on a older vehicle "causing the transmission to fail" just is not true, but it can speed up the process.
It is true ATF is high detergent, and if your old fluid is like mud, line pressure will be lower (like using 50wt oil in a engine to make up for worn bearings/low oil pressure) once you add fresh fluid. Another-wards, if your trans slips after replacing your fluid, it was already bad before you started.
I do not suggest flushing. Pan drop & filter change (if possible-some vehicles it is not). Your not going to get all of the fluid in most vehicles. If the fluid is discolored, change it out several more times (like when your changing your engine oil). Fluid is fairly cheap, and replacing the filter is not necessary if you just replaced it.... continue to do drain & fills until the fluid your draining out looks like the fluid your installing. (Note: if your vehicle has a pan & filter, I suggest installing a drain plug in the pan if possible to make the process easy.) Lots of differant fluids on the market today... read your owners manual and install the correct fluid. Some vehicle are VERY fussy over the fluid type. BMW's, VW's, later fords, Honda's. Make sure you research the correct fluid for the vehicle.
