When to flush coolant and what kind to use?

I was wondering when it should be time to flush out your coolant? I have heard that the dexcool that gm vehicles use slowly eats away engine internals overtime is this actually true? If so what would be the best alternative to use in our cars? I am currently at 76K on an 07 G5 Gt with the 2.4L le5. Thanks in advance!

Well I'm going to give this a shot; (If I'm wrong please correct me!)

Dexcool:
-was "eating through" gaskets (commonly 3.4L aleros or Grandams) aka Lower Manifold Gasket (GM fail).
-claims to be good for 5 years/100 000km. (IF left for more then this time period, it goes bad!)
-when flushing, use GM approved Dexcool (I know off hand Prestone GM Dexcool, silver container is one of them)
*If your planing on changing your anti-freeze make sure you flush all dexcool out! This is very important! Else "gunk build up" occurs, a chemical reaction between Dexcool and a different coolant.

Okay, first Dexcool is a great coolant. AS STATED - The problem was never the engine or internal components it was the material the gaskets used to be made of. The material reacted poorly to dexcool causing leaks and what appeared in alot of cases to be corrosion. Use what ever you like for coolant as long as it meets manufactures specifications.
On side note Dexcool is a silicate free coolant, this is a good thing.
If any coolant is left too long it will go bad, regular antifreeze should be flushed every 2-3 years, and long life every 5 years.

Oh ok, thanks guys for clearing that up.