a random thought...

When we go to heaven one day, it will be paradise again, with no pain, suffering, or sin. So, what's to prevent us from choosing sin again, the same way Satan (when he was an angel) did when he was in heaven? Is the paradise/heaven from Adam and Eve's/Satan's time different from what will be heaven in the future? Will we not have free will when we get to heaven? Any thoughts?
(so where did these random thoughts come from? was reflecting on Milton's Paradise Lost from an English class last year.)