When to rebuild the index?

Hi Guys,
 I think that even select statement will make the index split and require the rebuilding. Am I true? I think I am.  And there is a view called index_stats with column height.  I have read that when the value of this column is >= 4, u need to rebuild the indexes.
But after analyzing the particular schema, I don see any value to get populated in this view.
 I can see last analyzed value changed in dba_indexes when I analyze the schema with DBMS_STATS. ANALYZE_SCHEMA package.  Why this is so?
 Regards - Chirag

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