Kristine,
I do everything wrong and mine have lasted for a year. I don't wash them before I stick the transfer on. I only cool for 20 seconds before I slowly peel them off. I wave the shirt in the air like a flag and then lay it flat for an hour. No folding or anything. It cools flat for an hour.
I use Avery labels. Only Avery. Never used ebaby lady's transfer. Get mine from the supply house or Wal Mart.
I wash then inside out, cold water, Tide, Downy, line dry, no heated dryer, no ironong, just fluff.
My DD tossed the undershirts I made for the kids in hot water, Clorox bleach, tumble dry, balled up in the hamper. The transfers are still on, mostly bright. I love Avery..