That really depends on the game.
RBY is usually around 20-30h, because I'm usually abusing Spacebar a lot.
GSC is often over 100h, just because Red often requires a ton of grinding.
RSE is a lot less, usually 10-15h. Why? Because they can only be played at like 1/10th of the speed you can play the older generations with, so I spend less time running into walls.
FRLG is similar, but if I go for the second Pokemon league victory, it might take quite a while more.
DPPt are horrible, I usually need 30h and can only play at 150% speed (yeah, it says 200, but most of the time it isn't so...)
Edit: Dammit, I misread the OP. Wait, 15 HOURS PER DAY? Wow, and I thought I was playing excessively sometimes...
Well, again: it depends. Sometimes I play 5 hours a day and don't get bored, sometimes I play only like 10 minutes, sometimes I don't play at all.