Are you referring to Revelations 20: when Jesus comes back to Earth where there is a final judgement for eternity. Everyone only has one life. The final judgement brings everyone accountable for their own life.
Wikipedia has a decent explanation:
http://en.wikipedia.org/wiki/Last_Judgment
**Disclaimer: Don't take every word as truth, it is wiki after all :P
IMHO, preachers don't focus on the final judgment because how you live your life and the choices you make now is more important. Who God is and what He has done for us, what He is saying to us now is more important.
Occasionally final judgement is preached, though it’s not popular because it can be easily taken out of context and paints an incomplete destructive image of God. (i.e. If you don't believe, you burn in hell forever....)