BBD you make an excellent point about eating and sleeping a song before you even get a chance to play it. I do the same thing because I am the sole provider for my my family with two jobs and two little girls that feel like when I practice, they should practice also. My alternative is to receive the song(s) from my MD, listen to it on the way to work, while at work and on the way home. By the time I get home, I've got the song broken down, know the time signature, and have an idea for the loop I want to create. After I put them to sleep, I do the loop and sit down and play the song and work out the kinks.
When you can't practice, there are always alternatives. Air drums, etc. By listening to the song over and over, it really helps when my time is limited.