Totally up to you and them at the end of the day. Personally I wouldn't go near anyone that's 66 (25 years older) and I most definitely wouldn't go with someone 16. But 23 and 48, it's legal, neither is that young or that past it and if it works, crack on.
I've only ever been with anyone that's 7 years (I was 39 to her 32) younger, and 12 years older (I was 28 to her 40) - I enjoyed both experiences, but ultimately didn't have all that much in common with them, but that can be said about someone born the same day as you.
Just bear in mind you'll hit your prime when he's almost a pensioner, it might be great now but he's on a rapidly downward slope, and you're not even near your peak.