Anyone have problems with the charging system as it relates to burning through alternators?

I'm on #3. Luckily I Starmarked the car. All the ususal stuff MAF etc. I can't find anything out their about alternator failure. The MD Monkeys are replacing #2 with #3 but I have to think the problem is more serious?

ALSO, anyone have any luck adding additional Starmark Warrenty to an ML 430 with 91k miles?