Changed the tube and bought 5 spare tubes for a bike that is less than a year old? And you think you wore out a rim? What a piece of doo-doo. Or you just like throwing away your money on an overpriced piece of junk.
Next time get a coaster brake single speed and forget about all those brake pad replacements as well. You can paint it any kind of loud obnoxious colors you like for less than the price of five!! spare tubes.