DEAR CRABBIT - too old to debut?

Dear Crabbit
Is a 79-year-old debutant novelist (but a highly successful writer in other fields) deluding himself and wasting his time trying to get an agent or a publisher interested in his work, even if he’s fit, healthy and energetic, and has one novel completed and two well on the way? Or should he go straight into self-publishing? I’ve said “he” because I’m a man, but obviously it could