Thanks guys.
The heels had well north of 50 days on them. Bought in 2001, used with TD1s, F2s, and TD2s. The same heels survived a crash that ripped the cant adjuster out of my boots (Raichle SB) and broke my ankle in 2002.
Since recovering, I've been taking the alpine rig through the park for the past two seasons. I definitely landed pretty hard when it broke, but I know I've had harder landings and the heels were fine.
I'd imagine that the failure had been in the works for a while and that landing was the last straw. Not ready to give up on INTEC yet, I still think they are as reliable as toe clips. I'll just be checking them religiously, and going easier on the air time... :D