In some countries, rabbits need vaccines. I don't know how often (or if) they need boosters, but that would dictate minimally how often.
In the US, no vaccines are required. Unless there is an indication that something is wrong, I see no need to take my rabbits in for check-ups.
It's a good idea to do an initial check-up with a new rabbit. It's also good to go in if you suspect something may be wrong. But other than that, I don't see the need.