The point isn't just extending a vegetative state but a livable state. If life expectancy expands to 85, then you live comfortably until 65 or so. That means you can more or less be physically active just fine.

Look up on Google images old grandpa bodybuilders. There are 70 year olds that are stronger than majority of young men.

If life expectancy shifts upwards to 120 presumably the age of comfort also expands to 100, or what have you. Then it's a slow deterioration until 120 where you're basically a zombie. Of course this age depends on genetic variables as well as your personal health decisions.

My great grandma died this year at 100 and she was only a zombie from like 95. Until that point she was walking by herself and giving speeches, hosting parties, etc. 96 she caught dengue fever and lived, but was weakened. Then she caught covid a year later and lived, but was further weakened.

The final nail in the coffin was her falling and breaking her hip in January of this year. She was dead about a month later.