What is the life span of the solar system or the sun?

The sun has burned for approximately 4.6 billion years, and is expected to do so for about 5 billion more.

When it finally flares up into a red giant and then burns out, our solar system will be radically different: every planet will be freezing cold, and the planets Mercury and Venus (and probably Earth) will have been swallowed up and completely destroyed. The sun itself will have become a slowly-cooling white dwarf, with about half as much mass as it has now, compressed into an ultra-dense body about the size of Earth.

But after moving outward due to the weaker gravity of the less-massive sun, the rest of the solar system will likely settle down and endure as such until the end of time, or until another star happens to come close enough to capture some of the planets or otherwise change and destabilize their orbits.