I heard about this urban legend for a long time now. I think you need to change out the filter and fluid together. Make sure you change out the filter not, just the fluid. If it is that bad. It is a matter of time before it will give in any given moment anyways. Thought I would need a new trans but, found out that a 0.75 gasket by my mechanic. Changing the fluid and filter did the job. Voila, the trans is acting like it was previously. Though, my fluid was not burnt or brown. I have driven 160K on this auto trans with no significant problems. I don't think waiting will really help b/c you won't know when it will give out. It is better to know now than, later. The trans mech you went to probably, is awaiting for you to give up the trans and hope to gain your trust for, a more expensive job. The trans fluid change&filter and look over was, less than $100 at most. He probably knows that if, he resolves that problem compared to $2K vs. $100.