1994 Honda Accord V6 Automatic

We had a re-built transmission put in the car about 1-2 years ago. We returned to the establishment less than 3 months after the transmission was put in stating that the gear shifting was "rough." We left the car there for a check up and when we returned we were told that everything checked out great. Sometimes with new transmissions the car needs to adjust to the new parts. We brought the car back within the year with the same complaint, were told the same story. We've since brought the car back and were told that the problems we were having with the car (shimmying, etc.) Were the result of a bad transmission mount. They had to order one. We asked if driving the car while the part was being ordered would hurt anything. They said it wouldn't. After waiting quite a while we finally got the new mount put in (which they said was completely shot). This didn't help, in fact things got worse. Just yesterday they said that the torque converter is completely ruined and now we need another transmission. We were also told that a torque converter just "blows, goes out." Which meant that there are no symptoms of a torque converter failing. QUESTION: What are the symptoms of a torque converter going out or does it just "blow" without warning? How many miles can be put on a "failing" torque converter before it goes out?