1995 Chevrolet Lumina APV Transmission

Two weeks ago as I approached a stop light my 1995 Chevrolet Lumina APV (3.1 liter V6; four speed auto) felt like it was going over speed strips in the road. As I was slowing down, the entire vehicle felt like it was shuddering. When I went to go after stopping, I realized that the vehicle shut down. I put the van in neutral and it started right up. As soon as I put it into drive, it would shut down. I kept doing this, about five times, until the van started to move. It drove fine and then it did the same thing at the next stop light. Eventually, I had the van flat-bedded to a mechanic. He diagnosed it as the transmission lock up not releasing. He unplugged the TCC connector (he also referred to it as a solenoid). He stated to drive it and see if it happens again. He stated that eventually the transmission would have to be repaired or replaced. I have been driving the van for two weeks without any problems with the exception that I do not have overdrive (4th speed). My question(s) is: How long is the vehicle able to function this way? Do I need to have the transmission repaired/rebuilt/replaced within a short time frame or can I keep driving this way indefinitely? Should I just replace the solenoid that was disconnected that has to do with the overdrive? The vehicle has 104,000 miles. I have always changed the transmission fluid and filter every 25,000 miles and have never had any issues whatsoever with the transmission. The only negative issue is that the vehicle is 16 years old. You have helped me with other issues with this vehicle and I hope you are able to advise me the best path to take in solving this current problem.