Aging not fun. Not recommended. 2.5 stars. Don't do it. When you see 40 approaching over the horizon, just say no, turn around, and walk straight back to 30. You'll thank me later.
Feature, not a bug
Beyond a point of complexity, complex systems need to be designed (or evolve) to be made out of mortal parts. Immortal parts are a kind of arrested development. We don't know yet what natural lifespan for the human body design is, but it's not infinite