Come to think of it.
If we're immortal, we'd disappoint Einstein's law of relativity... and his quote "sit on a hot stove for a minute, it'll feel like hours... sit next to a pretty girl for an hour, it'll feel like a minute." (something to that effect)... y'all come across it?
... personally, I don't want to grow tired of my life, given that's actually true.
So, given my friends and loved ones are granted the same gift, I'd go for a solid 150 to 1000 years of life... not aging until the last 10 or 20 years, I guess.