I think you already know the answer, you have been doing it for a long time with many species and no ill effects. That's the answer.
Powerfeeding is a very naïve term. Unless you use a power gun and force food into their stomachs. If they feed on their own, it cannot be considers anything but normal.
What is a problem is under metabolized. That is, the snakes cannot reach temps(which support metabolism) to properly utilize the energy, so they store it as fat.
Also, snakes in nature may not have access to food year around so they do not follow a schedule anything like what most do in captivity. An educated guess is, a normal healthy wild adult colubrid like a corn or king, only requires about 12 feedings a yaar to maintain health and normal body weight. Another difference in nature is, they can lower their metabolism to conserve energy. Which they do year a round. So they do not burn as much energy as captives that are kept at constant warm then constant cool.
Whats missing by most is common sense and a normal base model. All snakes should grow long and thin(not skinny) and bulk up as they reach sexual maturity. They should reach 80% of their total length in the first year or two, then grow some after they become reproductive. That's with good support. A normal model in nature is 50%/50%, That is, they can become sexually reproductive at 50% of their adult length, then continue to grow is supported. If they have good access to food, they can do the 80%/20% as mentioned. What we see in captivity is often is a model based on poor shoe box keeping. While its understandable for commercial breeders to use minimal housing, its not logical for the average keeper to keep animals in such minimal conditions, muchless make rules based on SHOEBOX style husbandry.
