My '96 850 has had two alternator replacements - each about two years apart - one in 1998 and another in 2000. The car has 55k on it. I have noticed each time that when the new alternator is installed, the alt dash light, which cycles on/off upon turning the car off, will go out immediately after I turn car off. As months/years go by, the alt dash light begins to glow for a second or two after the car is turned off - I've taken this as a precursor to needing another alternator in the near future. Any suggestions what the problem is and how I correct the alternator eating habit.

Thanks.