How does Proverbs 2:21-22 not disprove "once saved, always saved"? For the upright will live in the land,
  &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;and the blameless will remain in it;
  but the wicked will be cut off from the land,
  &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;and the unfaithful will be torn from it."
  
  Proverbs 2:21-22 (NIV)


"The land" seems like it is the land of God, which might symbolize heaven. So how is the eternal security doctrine defended in light of these verses? Does it have something to do with the fact that they are in the Old Testament?
It is problematic to spiritualize verses too quickly.  Recall that the Proverbs were written by Jewish people living in the Jewish homeland of Israel under the Mosaic Covenant--not the New Covenant spoken of by Ezekiel and identified by Jesus at the Last Supper.

This proverb is speaking about upright and wicked people living in the land of Israel at that time.  Proverbs are general wisdom also--not incontrovertible truths.  Some upright people died young, and some wicked people live to be quite old.  

So, again, this is a general proverb that identifies that those who live righteously are often rewarded with long life.  The wicked, however, often receive God's judgment in various forms or are just exposed to greater risks for various reasons.

This has nothing to do with the New Covenant.