My father is 81 and is in a similar situation to your Dad's. The surgeon did not remove my Dad's urethra during his bladder/prostate removal last year either saying that the margins were clear and that Dad had been on the table so long (8 hours due to adhesions) that he did not want to keep him under any longer.
Now a year has passed and Dad has had problems with bleeding from the urethra since last July. His original uro kept telling him the bleeding would eventually stop. He finally sought a second opinion and had a polyp removed from his urethra last week, hopefully to stop the bleeding problem he has been having. The new urologist said there were abnormal cells in a saline wash he did of Dad's urethra but we don't have the pathology of the polyp back yet. The second urologist said it is likely that Dad will have to have the urethra removed and if it turns out this is the case, he will schedule Dad for the surgery quickly.
Dad's first uro wanted to take the urethra last month without performing any tests to justify this surgery. Dad didn't go for this and thus sought the second opinion. The second uro (who does over 80 cystectomies a year and also is a professor at a leading university hospital here in Texas) said that he usually does NOT take the urethra either UNLESS there is definite presence of cancer there when the bladder/prostate are removed. However, there is always the chance that there are micro-mets that won't show up until the disease has progressed. With bladder cancer, it is not out of the question that the cancer could spread through the prostate into the urethra.
Yes, I wish Dad's original surgeon had removed the urethra during his initial surgery. We weren't told then that he might have to have it removed later either. He had no positive nodes and did not have chemo either before or after surgery. Now he has an enlarged pelvic node and the second urologist wants to know how many nodes were removed during the bladder/prostate removal.
I don't want my Dad to have to endure more surgery either, especially at his age. He had to be under general anesthesia last week to get the polyp removed and didn't start feeling like himself for about four days. However, for my Dad, if the urethra needs to come out because of cancer or the chance of cancer, it must come out. With that said, I wish we had been told that he needed it removed earlier on in this process so he could have had it removed and not had to endure the bleeding problems he has had, not to mention all the scans and MRIs and x-rays, etc. We could have had all this behind us instead of facing more surgery now, a year later.
You can wait for symptoms to appear and then have the urethra removed, or listen to your surgeon and get it out now to prevent potential problems from developing down the line. Would there be time for your Dad to get stronger before the doctor wants to operate? I hope it all works out for both of our Dads.