There has not been a set mileage that failures have happened. There have been reports at 6500 miles and others at 90,000+ miles. The main issue with the CVT is its input adapter splines on 03 and 04's. Then Suzuki made a change for 05 and up that is a (SQUEAKIE) bit better. And some reports of CVT input bearings too. Yes the engine must be at least unbolted and dropped down for the CVT to clear the frame. Cheap bearings and under-sized adapters are the main cause!!! Better bearings and an adapter made in Poland ($250 + shipping) would make a 03 to 04 run to over 100,000+
Read the sticky on Primary adapters, LeDudes CVT repair thread, Buffelo's CVT belt repairs and many more.
Cheap bearings and under-sized adapters are the main cause!!!
THANK-YOU SUZUKI for engineering a fine product.