You're confusing two point: the meaninglessness of being simply atoms in the void, and our finite life spans. It's perfectly consistent to think that a finite life span would make us cherish our time more, if only not for the fact that everything is meaningless.
How that makes everything meaningless is totally beyond my grasp. It however mimics the message of 'doom' that some religious people uses to attack atheism.
Having read only a part of 'Gödel, Escher, Bach', I realize that the fact that we know some of the rules that atoms follow, and can predict how in average a given bunch of atoms will act, helps us nothing to explain how complex things form.
Never mind life, the most complex form of matter we know.
This in my view, makes all life (not just mine) very, very valuable. We are the most precious matter in the universe.
Most small things act 'in a way' when studied alone, but form incredibly complex patterns and 'behaviors' when acting in great groups that are totally unexpected, by anyone who studied the small things in single quantities.
In fact, a single brain will never be able to understand how a brain works. Thousands of brains, or a bigger electronic brain, probably can. But they themselves will never be able to explain how all the group or the electronic network works to produce knowledge.
Why should the emergence of complexity from simple underlying rules give meaning or value? First, there's the whole is-ought problem. Second, even if you tried to say complexity implied values, there are all sorts of things (computers, trees, and weather systems) which are highly complex but don't have the kind of intrinsic value that is assigned to people.
