Cell Phone Mythology

A couple months ago the battery on one of my phones stopped holding a charge. I took it into the store and they replaced it--despite the $5 per month I pay in insurance, I had to pay the full cost of $40 because the insurance somehow doesn't cover the battery....anyway, the clerk told me not to charge the phone all night because it begins to overcharge the battery and then it won't hold the charge. So I stopped that practice. Well, then recently my other phone stopped holding a charge. I finally took it in today and the clerk today told me it was the car charger. She said I should only use the car charger for 30 minutes max, even if the phone isn't done charging. I told her what the other clerk had said and she and the manager both disagreed. Supposedly it is safe to charge it all 8 hours of the night on the indoor charger but really is not okay to charge it for more than a half hour in the car. Go figure! (as a side note, it was OH SO nice of them to share this information when I bought the phone!)