Does he have an up-to-date portfolio on what he's been working on? how are his side projects?

I think that's one of the most effective ways to convince someone that you haven't been resting on your laurels/are still innovating.

Also, he could take the chance (assuming you guys are not 3 steps from being on the curb) to try and bootstrap a small startup -- 56 years is a ton of experience, he has to know some pain points in some markets/communities that he can fix (maybe his own?) and charge people money for.