I hate to tie up $900 in deposit for a year and a half
Don't be. Early December pricing is often unbelievably low. I remember pricing a Celebrity cruise for a friend in 2006 for early December. They got a balcony cabin plus a $200 credit for almost half of what it would have cost in the summer (without the credit).
I'd go ahead and book it. As CF notes, this could very well pay you a dividend in fuel surcharge savings since it appears they won't be going away and will only go higher - at least between now and the end of 2009.