Follow up: I got the re-done repair back from the shop. The person who did the work said this time he used new metal to make the repair. But he cautioned me, just like the shop owner had, that rust can never be permanently repaired. i reminded him that previous rust repairs from the same shop had lasted years, not months. I think the shop's contention is that no rust repair will last very long, and that Town and Countrys are especially prone to rust in the rear quarters due to the use of sound deadening material that holds moisture.
I do agree with DaveAdmin's comment about the huge difference among shops. This is the second time I have been burned by going on a shop's reputation unaware that their currently level of work no longer lived up to their reputation. First time was a shop where the owner's son had taken over, and the quality had slipped. They repaired collision damage to the right rear quarter pane of a six month old carl. The repair failed after 9 months, and by that time I had moved out of state and it wasn't practical for me to return the car to the shop. A friend of mine is an auto body man by trade. I asked him to take a look at the car for me to see what was going on with the repair. He communicated his opinion of the repair by putting his finger down his throat, and asked if I had a novice tech-ed student do the work. That was somewhat of a surprise, because the shop took over three weeks to make the repair.
The shop I used this time had done good work for me in the past, and the owner of the shop was still running the place. What I did not know was that I happened to catch him on one of the two or three days a week that he is on site. When the repair failed and I returned to the shop to speak with the owner and kept missing him, I learned from one of his employees, who said with some disgruntlement and envy, that the employees do all the work, get paid peanuts, while the owner is off enjoying leisure activities most of the week. Which I suppose is great for the owner, he invested the time, effort, and risk in starting the business, so if his reward is to be semi-retired - good for him.
I agree with DaveAdmin that there can be a significant difference in quality between shops, but how does one learn which shops to avoid when your are not in the auto body or insurance businesses? Even when you have first-hand experience with a shop, if you don't have recent experiencw with them, you may come to realize as I did that their quality of work has slipped.