I am coming to US in B2 (tourist) visa. I am flying on April 10, 2012 and my return ticket is on Dec. 10, 2012 (exactly 8 months apart). I am hearing that return ticket should be within 6 months otherwise I will not be allowed to enter at port of entry. I asked this question to US embassy in Kathmandu but they did not provide me the substantive information on this. Please share your experience if you have deal this situation before.

Thanks!!!

 I would strongly recommend you to have the return tickets apart not more than 6 months. Visitor should have strong/motivating rationale to explain if you intent to be here for more than 6 months. This is somewhat tangential and do not entitle you to receive stay peoriod for more than 6months, if not less. As of USCIS, B1/B2 cannot get stamped (at port of entry) for more than 6 months per entry time. Which clearly indicate that if you enter with returning tickets beyond six months than you are likely to ask return or will face vicious immigration consequences. Being said that, you can apply for your extension if you wish to stay longer (as long as you have valid VISA beyond the extension period). 
I am trying to share my experience to the best of my knowledge, and do not gurantee that this is 100% correct. Let some sajhaiyatees speak forward who might have better suggestion for you before you make a solid decision.
Good luck