Well, in 24 episodes he had repeated many artists and sometimes of the same record, so I won't bet there would be more. If he had really so much music, there is no need to repeat artists so many times...
I have a collection of about 3,000 songs, of which I would play on the radio show, if I had one, about 500. Mark, at 71, I think has like 30,000 songs on his jukebox, he lives for so long and he is in the business for so long that I think he can go on with this show forever. The fact that he played so many repeat apperances and similar folk pieces is just because he really likes it...
Hovewer, when I was putting my own playlist I thought I would not pick several tracks from one album, if that album is not a freaking masterpiece. Because that would be boring for me, let alone for the listener. But Mark is the boss, no complaints here.
For now it seems like 24th is going to be the last episode, which upsets the hell out of me. I hope this is really like one of these shows that says "Here's the final episode" and later go out saying "Hey, welcome to the second season". But honestly, the show is so underrated and ignored by fans, that it might as well come to an end. So many people I know who either don't care about Broadcast at all or don't know about it. So I wouldn't be surprised.