I think that it is only fair to let him have a little time to adjust, as long as he isn't seriously hurting himself. I agree that you need to monitor his quality of life, but as long as he is doing well, is happy, isn't losing weight because of stress ect., there is no reason he can't live for a few more years at least, as a happy healthy horse. We had a 35+ year old horse (vet actually said that he was probably older than that, but based on his teeth, he was at least 35), who was still jumping small jumps, barrel racing, going on trail rides, ect., and loving life, never had an unsound day except when he has absesses, but he finally colicked one night. We gave him the night to see if he would get any better, even though he was old, but we did have to put him down the next day. We don't regret at all spending the extra bunch of money to keep him as comfortable as possible during the night to see if he would get better, even though it would have saved money if we had just put him down when he first colicked. Sounds like he's doing better though, and hopefully he'll work everything out.