Originally Posted by operator

Get back to us when you've worked for a high volume road shop, for a while.

Home wrenching is completely different than shop wrenching. And your experience, unfortunately does not reflect reality. Cables will fray usually at the anchor point where they've been crushed. Rear Derailleur cables especially will tend to break off at the head, leaving the rest stuck in the shifter. This is not good for shimano STI's.

Brake cables are much more durable. You don't need to replace these periodically, only when there seems to be a problem. You'll likely get contamination/rust that requires replacement before you break one.