Long is most common in questions and negative sentences, and after too and so.

• How long did you wait?    
• I didn 't play for long.
• The concert was too long.

In affirmative sentences, we usually use a long time.

• I waited (for) a long time (I waited long is possible, but not usual.)
  
• It takes a long time to get to her house.

Much, many and far are also more common in questions and negative sentences.