It really depends on the health of the rabbit. Older rabbits can be a bit higher risk for the anaesthetic, but a young rabbit with a health problem could be more of an issue.
When the rabbit get to be around 5, then it can start to be a bit more risky, but can still be safe if the rabbit is otherwise healthy. After about 7-8, it might not be a good idea to do the surgery unless there is a reason like cancer where the surgery would take care of the problem.
If you have an older rabbit, then you need to talk with your vet about the risks and the general health of your rabbit.