I haven't taken the 15 minute break EVER. Not even when I was 3 and my mom told me my cat died while I was playing Mystic Quest on SNES. Just cried and kept playing (probably not the healthiest of coping mechanisms).
As for how long I will play it ... When I first get it I will probably play for 5-6 hours that night and then whenever I can after that. On Thursdays I can play for almost 8 hours at work and usually do so with only one or two breaks for water or to use the bathroom.
I only laugh at pain, and it's about to get real funny.