If one gives up ego, one gains everlasting life -- the spiritual rebirth that Christ mentioned.
Ego is the blindfold that brings darkness to the true, spiritual self and makes us dependent upon physical senses of our bodies.
I would very much like to be rid of ego once and for all. I have tasted this, and I could see without the via of human eyes. I could maintain conscious awareness without the human brain of my current body.
With this -- spiritual rebirth -- I pick up where I left off so many millennia ago, in the Garden. I regain my immortality, so I "live" for an infinite number of years.
As for your interesting question, I might pick 20,000 for my physical body. I would expect that the body rejuvenated itself and kept a clear eye and mind, as did Moses to 120. At 63, I'm still in pretty good health. But my main interest is in eliminating the ego self so that my true self can be reborn once and for all. For only then can I truly follow Christ. I hunger for this.
As for why I would choose 20,000 or 2,000,000 or even 2,000,000,000, I would love the continuity of conscious that would be unnecessary with a physical body, if ego were fully gone. I would love the experience of seeing so many changes -- seeing the growth of civilization, perhaps. If only we can get past ego, civilization could last. But I think this physical experience will not serve us well, once we have achieved spiritual rebirth. Living in an action-reaction world would tend to perpetuate the action-reaction, ego self. Perhaps, it would be best to return to God and leave all attachments behind.
I sometimes wonder what would have happened if I had not died 11,553 years ago amongst the other refugees of that once proud island. It would've been quite an experience to see the "elves" of magical, lost technology mixing with the primitives of post-Ice Age Earth. It would've been strange to experience the rebirth of civilization more than 6,000 years after the previous one had died. And it would've seemed like an eternity before technology once again became common. But through it all, the sameness of ego would show that humanity will remain the same so long as selfishness and separateness remain.