Car batteries should last for 10 years. If not, you have a bad charging/electrical system...
15 years ago that would have been a reasonable statement. Today, not so much. Electrical demand in modern cars has skyrocketed, alternator charging capabilities have risen from 90-100A to 180-220A on the average luxury cars we work on, some alternators are liquid cooled to keep up with demand. Power control modules are replacing voltage regulators, and battery replacements are now "registered" to the power control modules using the manufacturer specific software. The negative battery cable now includes an IBS, or Intelligent Battery Sensor that communicates with the Power Control Module. Batteries lead a much harder life in the current crop of cars than they used to due to much higher demand and much more amperage being put back in more quickly. I'm seeing 5-7 years now as the average life expectancy.
