As an ancillary point, there is no such thing as "aging in good condition". Aging is the process by which your body gradually fails to function until it can't function at all. It can be better or worse, but not good.
So difference is live one life to 500, or
Live 5x100. Come back at 10 or 1 or whatever. I know this idea is totally fantastic, but, as a thought experiment, I'd prefer this.
I think you've just described everybody as they currently exist. there's a lot of memory from childhood that my brain has stripped of detail and archived; probably more that I don't even know I've forgotten.
This does not fill me with existential quandary. I look at my hands, and I'm still here. shrug ;)
Memories don't randomly vanish; there's pretty good evidence that the brain does retain useful content. So if you're arguing that "500-years-in-the-future you would be such a different person that we might as well say now-you is dead in 500 years," I think the burden of proof is on that claim because we don't make it for modern elderly people. It passes neither the common-sense sniff test nor the extrapolation test ("What's special about 500 years out as opposed to 70 years out that breaks continuity?").
Reversing aging will improve your quality of life, but will also force your death to be brutal, since the only cause of death is now accidental or some illness. So you'll die not wanting to peacefully go away as people aging in good condition do, but you will die wanting to live, hurting badly. I'll stick with buddhism.