There's no correlation between driving long distances and battery life. We can only hypothesize that the alternator has finished "recharging" the battery from long trips versus the short trips and this leads to longer battery life. This is because frequent starts coupled with short trips leave your battery.. well... short.

And no, it's not using your car leads to premature failure but it's the fact that your battery needs to get a charge every now and then as your battery discharges itself naturally. I can have it hooked up to a battery charger and not use my car for 3 years and it'll still be okay.

And before we veer off-topic, yes, your resident Tsikot car audio section spammer is Amaron powered. Not that I'm convincing people to get it but I do recommend it.