It's a good idea to incorporate some form of unarmed combat along with your weapon techniques for defense, and martial arts is a good way to do that.
Like a few folks here, age has crept up on me too, but experience in various arts has helped. Unfortunately, I never stayed with any one system long enough to really master one, and that I regret. I formally studied Tae Kwon Do for 2 years, Fu Jow Pai Kung Fu for 2 years, sport karate for 1 year, boxed amateur for over 5 years and had exposure to wrestling techniques in college. And my training in security/protection field has exposed me to take-down, cuffing and baton techniques.
Mastering weapons retention and disarming skills is certainly something that can benefit your firearms skillset, and some arts can help with this. Also, it's good to know some knife techniques as backup.