I see a potential problem.
Let's assume a 64kbps audio stream. (I'm guessing.)
7:00am - midnight = 15 hours.
15 hours = 61,200 seconds.
61,200 seconds x 64000 bps = 3916800000 total kilobits = 489600000 kilobytes
So, a 64k audio stream playing for that time would equal roughly 466MB
That's a LOT of data to pushing over EDGE in a single consecutive stream and I wonder if AT&T would view this as "abusive" use of their network.
Networks have been known to cap bandwidth usage for various reasons.
If they look unfavorably on your usage... they may decide to pull the plug on ya.
Maybe not bad for your phone... but could be bad for your account.