Originally Posted By: danthaman1980
I usually replace mine every 3 years... The Texas heat will kill batteries - if you get 5-7 years out of one down here, you're very fortunate.
Its also a good idea to have the alternator serviced at the same time, especially if you're up past 100,000 miles. Alternators don't last forever - I'm on my third set of brushes, 3rd regulator, 2nd rotor assembly... and only at 170,000 miles.
The alternator in my LS400 didn't get replaced until 200+k miles, the problem was PSF leaking down from power steering pump right on top of the alternator and short it.
The alternator in my 130+k miles in E430 is original, and I don't plan to do anything to it yet. Checking the voltage with engine at idle it still generate 14-14.2 volts.