Lets see...
Only about 12 days for me.

12 days 2 hours 36 minutes and 31 seconds
epicsoundz69 Reviewed by epicsoundz69 on . How Long Can You Make It Last? Simple enough, I'm wondering who has itunes packed with so much music it can go an obscene amount of time without repeating. Myself, a humble 25 days: 19 hours: 15 minutes: 28 seconds What about you? Rating: 5