2 destroyed starters in a row...WTH?

Thanks for all the input guys.

One of the first things I thought of was kickback with too much initial timing, but something that's confusing me a bit is the fact that my combination worked fine for the first 6600 km until it broke, and then broke again only 400 km later. All this time, the timing never changed from the original 10-12*initial, 34* total, which was checked right before the 2nd failure.

I'm wondering if some other malfunction started sometime before the first failure - like the Distributor going haywire and sparking too soon when the starter was cranking? Just a hair-brained theory, but I'm stuck wondering why this issue has come up "all of a sudden" with no other apparent changes?