Hmmm...
I was unaware that scientific studies had been done linking "overfeeding" with shortened life span. Please do not throw out dribble like this without at least adding that it's your opinion.
Taking into consideration how little is known about snake physiology, how few snakes are necropsied and how few vets actually are somewhat knowledgable in the herpetological dept, I'd say this assertion is a bit premature.
What exactly is the expected life span of a captive ball python? We don't even know for sure how long they live in the wild. What other variables can affect life span...genetics, type of food, illness, reproductive efforts, gender...
We do know that they CAN live UP TO forty years or more in captivity, but you know what...not near enough ball pythons have been raised in captivity or tracked in the wild to make a difinitive figure.
People have been known to live over 110 years, but the average lifespan is 70ish. Horses have been recorded in their forties and ponies as old as the lower fifties, but the average lifespan for a horse is 20.
It's going to be a couple decades before anyone can make that type of correlation with any authority. For now, I suggest feeding how ever you choose, but keep good records that might lead to the conclusion of this debate once and for all.