My Protank II coils last me months. I have some that are at about 3 months right now and still going fine.
I do as suggested in an earlier post. I have 5 coils total in a rotation, I take the coils out of the Protank daily and put them in a Tuperware container. When I have 3, I soak them in vodka for a few hours - overnight, rinse them with really hot water and let them dry overnight-up to 8 hours-ish.
No dry burns, no alterations to the Protank and whey they are toast, I put them in the "if I ever decide to rebuild a Protank coil" drawer.
Rebuilding coils takes some more supplies and a desire to tinker with stuff. I have never found an alteration that worked 100% of the time and dry burning has always been a waste to me. You can buy a pack of 5 for like $6 plus shipping...............if they go bad, you can just replace them. Some are duds out of the box but maybe I am lucky, I haven't had one of those yet.
EDIT: If you are going to buy coils, buy the legit Kanger coils. They come in a Kanger box and the grommit (the part between the bottom pin and base) is clear-ish. Knock off coils are the root of a lot of people's issues IMO