I've only driven my Syncro for a year. It took over a year toget it ready and I'm not sure at which point I rebuilt my rear half shafts. At best, they're only two years and about 10,000 miles old but I'm finding that several of the boots are already cracking significantly. These where Rhein boot kits purchased from ken willford. 
What could cause this aggressive decay and how can I prevent it?

-craig