Training

Chip with all the riding you do, just replace your cables/housing every year and this should greatly reduce your chances of a failure.

I feel that you should not go more than two years, max, on a set of cables and housing without some form of service or replacement. Not just the risk of cable breaking, but shifting and braking get sluggish as fine dirt slowly collects inside the cable housings, slowly degrading the whole quality of your ride experience. One way to extend the longevity of your cables and housings and spread out the expense of replacement is to at least once a year (when you are doing a complete teardown and cleaning of your bike, right?) "rotate" your cables and clean the housings. What I do is buy one new deraillieur cable and one new brake cable, take all the cables and housings off the bike, throw away the front brake and derailleur cables, inspect the housings and replace any that are damaged or too worn. If the housings look good, clean out the insides by spraying some WD40 into the housings to rinse out the dirt, then rinse out the WD40 with water (I blow some mouthfuls of warm water through the housings like blowing through a straw until the water runs clear, if you want to be really finicky, suck up and blow out some warm soapy water repeatedly before a final rinse with clear water). If the rear brake and derailleur cables are in good condition, clean them off with a bit more WD40, then rub a good dollop of grease over the cables, leaving a good coating on the part of the cables that will be inside the housings (I have been a longtime user of Phil Wood grease for everything on a bike except the chain). Reassemble the front brake and derailleur cabling using the now cleaned and lubed rear cables, they will be plenty long enough for the fronts. Then you use the two new cables you bought for the rear brake and derailleur. Trim all the cables, put on some fresh hot tips, wipe the exposed parts of the cables lightly to remove any excess grease, and you now have your "new bike" feel back for less than $20 and an hour's worth of work, and you greatly reduce the risk of on-road cable failure. You should still replace everything after a couple of years, as the housing liners do wear down eventually. And all of this is assuming that you have lined housings on your bike. If you do not have plastic lined housings, then get some.

Last Saturday on the Mystic ride, my rear derailleur cable broke about an hour in while we were in Preston.  Thanks to Mike Kennedy for making sure I had tools and a cell phone.  I made it home in my 34 x 11 no problem, but was bummed to have to bail on my only group ride of the week. 

The cables were original since I bought the bike in early 2007, so I got more than 3 years usage.  This week I had all 4 cables and housings replaced.

Mark Dutka had a cable snap in a race earlier this year, which prompted me to replace the cables in my everyday road bike, but for some reason it never occurred to me to change the cables in my race bike (duh).

The rear derailleur cable takes a lot of abuse because of the number of shifts and the routing in the shifter.  I wish I had done some preventive maintenance to change this, instead of having this break during a ride.

Chip