I find I get "burnt-out" in GM when I make GMing my main focus in life. If I drop everything else and exclusively make games then after a week or so I'll run dry. I usually get alot done in that week, but reach a "programmer's block" right after.
If, however, I view GMing as a hobby (which it is) and balance it with the other aspects of my life (school, work, girlfriend, friends, guitar, playing games, getting sleep) I'll be much more enthusiastic about it when I get the chance to open up GM and start coding.
This is the same thing with me. Even though i have only used GM for a year, there was one time, when i made GM my main focus in life only to find i lost inspiration and became of bored of GM. But when i balance with other stuff in life, yes i get more enthusiastic about programming my game.