59 Minutes - Bonkers! 11, CD3, DJ Scott Brown, continuous rave/house mix.
I wanted to see if I could stealth it after 1 hour, ended up with 2.9mill and 99% of blocks collected, in Casual Mono. The whole thing averages about 50k / ppm.
I believe the max allowable time is 1 hour, as I couldn't play a couple mixes that ran just over an hour, and they were only at 128kbps. Maybe it's a size issue, this 59 min song was 55mb, while the others I tried were 70mb. It would be cool to know just what the max is (either in size or time), just so we don't have to bother trying songs that won't work.