What I do is to replace the battery after

first time cold weather start failure if the battery is more than 3 years old. It's not worthy of stretching the old battery little bylittle, especially in the northern states. Imagine you have a choice of getting stranded in a cold stormy winter day for two hours (normally when you are stranded in such a stormy day, towing service is very hard to get; it will more than often to cost you a whole day) or paying 60$ staying in your cozy warm home. What would you prefer?
Simple choice for me; hopefully simple for others too.