As far as places to get them cheap are concerned, check the suppliers forum here. Don't want to list any here, as there are always sales popping on and off. Find a sale from a vendor listed on ECF, and you should be in good shape.
Try your attys on your fiance's battery. If they work, then its a problem with your battery. If the battery was a cheapo, it did cost less, and will tend to die quicker too. Yes, attys like to be inverted onto a paper towel at night to drain of excess juice. They also don't particularly light high voltage, even if you do. But your eGo is not high voltage.
If you have a multimeter, you can check their resistance. I set mine to 0-200 ohm range, beep mode (no beep means coil is broken, atty dead, bye bye), and put red lead to center battery-thread hole, and black to outer threads. If you are reading higher than about 3.3 ohms, it will likely be too weak on an eGo (~3.2V). It should be in the 2.4 - 2.8 ohm range, unless it is low resistance, and then it will be lower. Not much vapor happens above around 3.2 ohms.
Keep any atty wet while
vaping. Burnt flavor means dry coil, which means overheated coil if you keep
vaping, which means shorter life, but then with attys you are always looking for that burnt taste. Make sure the cart wicks juice properly. Carts are notoriously bad at wicking juice to the atty (and its the only thing they are designed to do!)
I clean mine in polydent overnight denture tablet solution, then after about 12 hours flush with hot water and dry either in open air or in a 250 deg oven. A clean coil is a happy coil. Gunk on the coil will tend to increase resistance, and thus lose vapor power.
But again, it sounds like it could be the battery, not the atty, although if you think you have been abusing yours, you probably have. They are pretty rugged, but then their working mode is pretty rough on them, even when clean and healthy. Toaster coils don't last forever either.
Good luck!
