1996 Toyota Corolla

190,000 + miles

Transmission fluid high on level stick and after talking with mechanic he mentioned possibility of needing transmission rebuilt in future so to start saving. He took some out and put something in to possibly help or clean it out? Then told me to recheck level accordingly/periodically. I waited a week and it was high again. What kind of time frame before a possible breakdown? And how much usually for a rebuilt transmission? Anything I can do to delay the enivitable? I have not done anything past just checking the transmission level in all the years I have had it (that I can remember). Any advice is helpful.

Thanks,
Michelle.