{snippage taken}
Mike Jacoubowsky wrote:
I wrote:

My Ultegra 9 rear shifter broke off a cable head at least once; and
my Dura-Ace rear brifter -- replaced once under warranty after
breaking off a head and then crapping out -- broke another one just
last week. Got the head out after some doing and it seems OK now,
but that's at least 3 gear cables that have lost heads (might be one
more) on two bikes in 3-4 years.

But how many miles of use? 7,000 miles would be a fairly normal
lifetime for a rear shifter cable, based upon my own personal
observations. I actually do better than that, but I try to make sure
they're running smoothly and keep them lubed at the bottom bracket
cable guide (where drink mix & road gunk conspire to create friction).

Yes, guilty as charged (gently as it was). This last time, for sure, I
ignored signs that there was a problem (shifting got sketchy and I just
adjusted cable tension) and paid for it by single-speeding 20 miles home.
(Too lazy to use limit screws. God gave me a triple for good reason.) Not
sure of mileage before break, but way over 7,000 I'm sure...

Bill "and let's not discuss ignoring CHAIN wear" S.