I did some research into living forever at one point. Basically, three things kill us: Disease, old age, and trauma.
Disease seems beatable. Reversing old age is going to be trickier, especially as things we don't expect to fail start failing after we prolong our vitals for longer. But these both should be doable.
The real killer is trauma. I scubadive. Given forever, eventually I'm going to something stupid underwater and that'd be the end of me.
The 200-300 years seems like a good place to start. It'd involve preventing or treating fatal diseases and finding ways to keep especially your vital organs running. I started spending more time in the gym and eating a bit better after my research.
This could be solved by perfect VR and disposable bodies grown in a vat, with a remote control system instead of a brain. Your real body hibernates and your real brain can think its scuba diving, while only having to worry a little about getting eaten by a shark (it would probably hurt).
I think the sci-fi version of this in Doctorow's Down and Out in the Magic Kingdom is about the best -sounding- version of this sort of scheme.
You regularly make 'backups' of your brain and if you die your last 'backup' is loaded into a clone.
You (the new you) of course, don't remember anything that happened after your last backup. Made for an interesting plot device as well.
