Our boxer who is 10 tomorrow!!!! A few years back tore his CCL. Our vet said he did not tear it that bad and with R&R (doggie downers work wonders!) and supplements he would be near normal, never would be 100% but close, we asked to do surgery anyways and were told no. He told us that it would be a sure bet that he would tear the other while recouping and instead of paying once we'd pay twice. Needless to say our boy is fine and even though he is going on 10 he still acts like a puppy, we just watch him very carefully and don't allow him to tear it up outside anymore which sucks because my parents have a 4 year old boxer and they love to play. Obviously if we were told he needed the surgery we would have done it in a heart beat and if the other one tore we probably would have done that one too.
It's hard to tell someone what to do in this situation, We love him and for all purposes he is our son, but it becomes age vs quality of life vs bank account. I know if he was 10 & was in pain all the time or were told it wouldn't be worth it, we would probably think twice.