NOW...you can book tours up to 1 year in advance. While I haven't personally been on this one, from what I've read about it, they only take a limited number each day.
We've already booked our Family Magic Tour for December!
I booked yesterday for Keys to the Kingdom Tour for June for our upcoming Anniversary Trip. You have to pay in full - but you can get a full refund if you cancel before 48 hours (or something very close to that). I booked the Tour before I even booked airfare or hotel!
Agree. I finalized our Sedgway Tour in EPCOT and the KTTK tour today for late June dates. The only reason to wait is if you want it to hit your credit card a certain month. The KTTK is really reasonable with the 20% discount for Disney VISA holders. You get a 48 hour cancellation policy, so I say go for it before your time slot gets filled up!