How far into the cast is Swallows of the South. I'm going to be horizontal on a beach for a few days and I've been saving the DMB story times to listen to, but I might splice that in as well if I have time.
They are give or take 60 episodes into the show. Quinn's advice is to just jump into the second arc if you want to, and the show takes a more serious tone around episode 8/9 of that second arc. Definitely a decent back catalogue for you to listen to.