For Oz we had title music (which played on the map screen and book screen also) about 1 min. Level complete music, about 30 secs. (If there was a game over state, I'd have wanted music for that, about 30 secs). There a short piece for game complete that hardly anyone will hear, shame. Then 5 level pieces 1-2 mins long (1Mb @ 96Kbps ogg). I personally find it disappointing when a game only has one in-game piece of music and no variation, same as no variation on the game background. Oz changes music/background every 5 levels, and my Xmas/Easter Bonus games change *every* level and so will my next one.
Variety is good I think. But yeah it sure boost the file size, the oz music folder is nearly 7Mb, bigger than some whole games!