The only possible benefit is that you know the "attacking" IP is a "bad guy" or compromised machine, and probably don't want to talk to them anyway. It's likely they'll try other protocols. If you have none open, nothing to worry about.
It might reduce bandwidth slightly. It would definitely reduce the spam in your logs (I change my SSH port to 2222 for this reason; but don't recommend that tactic unless you have a small group of admins accessing the box).
It's technically possible that they could guess a SSH Key, but wholly unrealistic to think it will ever happen. I would recommend changing your SSH Keys every few years (to ensure you're using "current" technology, and to verify documentation surrounding the system).