Using addative for seal leakage

My front trans seal was leaking after the engine got very hot,
would go through winter without leaking at all...but anyway, I
used a transmission addative ( green bottle, cant remember
the name...I think Transmedic maybe...) The seal would still
leak the first summer but this summer it has not leaked , so I
assume the seal has expanded enough to prevent the leakage.
My question is now that the seal is working, should I change the
fluid to remove the addative......Will continued exposure to the
additive cause a problem with the seal? I know you experts will
recommend having the seals changed and I plan to but I don't
want to spend that $500 until I have to.

If the leak has stopped and the fluid level is up to par, leave it where it is. When it starts leaking again, the sealer will not work again. Then you will need them replaced.

If it ain't broke, don't fix it. If you've run, let's see here, two years? 18 months? Without a problem, I'd say things are going fine. Changing the fluid now risks disturbing whatever is holding the seal together (though it's a slim chance, it's still there), so better leave well enough alone -- unless a problem develops.

Good luck.