Musicians like that are very hard to keep up with, but if they are good, not just full of songs (and themselves) and you are willing to do what it takes to keep up, you will find that they will really prepare you for being a 'fits into anyband' musician yourself.
My first cover band was an experience like that - I was a good 8 years younger then the other members who played a full list of pop/rock/light dance jazz from groups like Spyro Gyra, Steely Dan, The Cure, The Violent Femmes, The Bussboys, and on and on... We even did School Days - but I don't wanna talk about that

... I was only 19 when I hooked up with them and took it very seriously sitting in my parents basement with the tape for hours, picking out every line in great detail. When I did my first jam with them they all expressed their surprise with how thoroughly I learned the stuff - but that was how I was taught by my high school experience - learn your stuff! Learn it right. I went on to play with that band for 10 years playing corporated gigs for Budwiser, Riverboat Dinnershows, Golden Gloves Boxing matches as well as the good old bar circuit.
ANYWAY... Every other band I hooked up with since that band has been a cakewalk. So, if you can keep up with the dude - buckle down, learn the stuff and treat it seriously, it will pay off in spades down the road.
--tz
PS - all you youngsters... back in the day, we had to use good old cassette tapes - pause, rewind, play, pause rewind play... damn, I want to work on a song 10 songs in... ffwd.... stop, check....
I LOVE LEARNING SONGS TODAY using MP3s, CD's, pitch-shifters, multi-track software and so on... The tools and technology today make learning covers SO EASY. Not to mention, TABS...