Anything that causes them to work hard, especially in hot weather, can kill them. This is why I don't really like DRLs. It's also a good idea to do a voltage test on your battery occasionally, because if it's not taking a full charge, the regulator never shuts off and the alternator charges the entire time the engine is running.
Some people drive around all day with their headlights on, not giving a thought to where that energy is coming from. I only use my headlights at night, I don't do major stereo upgrades, and I don't do anything that causes any significant battery drain when the car isn't running. I've also never had to replace an alternator.