I don't think it is meant as a comparison
The point is more: you will not live for a very long time, so why waste what little time you have on futile things... er... like this post...
*thinks about what I've done*
( tangledupinblue hairy badge with moving eyes, Thu 19 Jan 2012, 12:11, 1 reply, 14 years ago)

Yeah, but life is the longest thing any of us will ever know
so perhaps it's not the best way of expressing such a sentiment
(Darth Foxtrot A one-man army dedicated to making fetch happen, Thu 19 Jan 2012, 12:15, Reply)

Unless you get Alzheimers

( sporters I’m sincerely gratitude to you, Thu 19 Jan 2012, 12:16, Reply)

You can't cope with concepts of time longer than your own life, Trotter?
Anyway, I prefer the more pessimistic version of the phrase: You're a long time dead.
( tangledupinblue hairy badge with moving eyes, Thu 19 Jan 2012, 12:20, Reply)