Just out of curiosity, what kind of charger are you using? The chances of you getting the same defect 4 times in a row are really, really slim (sorry for the lame pun).
Not sure if you are using a wall charger, a car cigarette lighter charger, or a power bank but I'd use a different charger, and cable if I were you.
FYI, my slim and my slim+ have been getting regular use and have been going strong for a few months now. I've even used a forklift battery (connected to a 36v-5v buck converter of course) to charge my earbuds with zero problems.