98 Buick LeSabre with 88.5k miles. Tranny never abused to my knowledge (bought from little old lady at 35k miles, wife has driven it since). I do not know if ATF or filter has ever been replaced (yes, I've been lazy); however, fluid is perfectly red, sweet, and has absolutely no specks or particles in it. There is nothing wrong with this transmission--no grinding or abnormal slippage--it is just a bit "mushy" for my liking.

I will soon be dropping the pan to replace ATF and filter (and also adding a TruCool tranny cooler), and I am considering installing one of the "do it yourself in the driveway" shift kits while I'm in there.

Main objective is to prolong life of clutches. A distant secondary objective is better performance (Note that this is a daily driver, and I am NOT looking for "bang, screech"--at most, I just want improved overtaking when entering / passing on the freeway).

I currently have NO plans to do any other performance mod upgrades from stock (intake, catback, PCM, fuel or spark), if that has any bearing.

I kind of have it narrowed down to either the Transgo 4T65E-jr kit or the Thrasher 4T65E kit. Here are the pro'* and cons of each, as I see it:

Transgo:
Pros:
Cheaper ($55-60)
Comes with accumulator piston o-rings
Cons:
Does not appear to include accumulator body gasket (can anyone confirm this?)
Does not appear to have as many "performance levels"

Thrasher:
Pros:
Comes with accumulator spacer, filter, and free T-shirt
Although not pictured, an e-mail response from 3800-performance claims it comes with accumulator piston o-rings (can anyone confirm this?)
Many "performance levels"
Cons:
More expensive ($90-$100)

So, to those who have installed one of these kits:
-How likely is it that the accumulator spacer will be damaged / need replacing?
-How likely is it the accumulator piston o-rings will be worn / need replacing?
-Based on my criteria, which of these kits (or an alternative suggestion, or "don't do it") is the right one for me?

Thank you.