I've broken brake cables. My winter/city bikes get used hard and see very little attention (and not a whole lot of daylight for 4 months of the year). The culprits are usually bends that are too tight or chafing where the cables enter and leave levers and stops. Aero levers with hidden cables under the bartape can be the hardest to notice.
I"ll second the every year cable replacement for a one handed rider. Maybe more often. I put this in the aluminum handlebar and stem category. Replacing too soon costs money to the tune $10-100. Replacing too late could well be thousands (medical expenses, etc). The time scales here are obviously quite different, but so are the replacement expenses.
Be a geek. Obsess on those cables. And keep coming back to the forum so you can share your rides!
Ben