[ACCount37]

This. Expecting a "150 years lifespan" to look like "90 years of aging normally and then staying at 90 for another 60 years" is simply unrealistic.

The very reason you're expected to die in your 90s is that your body has decayed into a complete mess where nothing works properly anymore and every single capability reserve is at depletion. You die in old age because if you spend long enough at "one sliver away from the breaking point", statistics make going over it inevitable. Even a flu is a mild inconvenience to the young, but often lethal to the elderly.

To make it to the age of 150, you'd pretty much have to spend a lot more time as a healthy, well functioning adult.