I've actually been told I'm not power feeding when I feed on a 4 day schedule. Some people don't consider it power feeding unless you are feeding every 3 days. Power feeding is not going to kill your animal, stunt their breeding, and I highly doubt shorten their life span. I can't be sure about shortening their lifespan because that takes 20-30 years to figure out. The only true thing I've heard/read is that fat females tend to have a few more slugs and fat males tend to be lazy breeders. You should know if your animal is obese, white will be showing between their scales-that is their skin. If your snake ever gets to that point, cut back on the feeding schedule, problem solved.
Also, I don't think 350 is a terrible weight for an animal that age. I have a het pied trio that are about that age and size because they only eat when the feel like it. It's really frustrating! I also have females the same age that are 600 grams. If you aren't breeding and she doesn't look skinny there's no reason you should stress about her gaining a bunch of weight.