Hi

Indeed this has been covered before and was especially more of an issue on 2008 models and most of the 2008 bikes had the modified 2009 breather expansion box as did I and the change corrected the problem for the 2008 year bikes. If you get a little oil then don't worry too much as I use to get a full outlet tube of oil after about 4-500 miles. Its caused by high speed riding over a few miles. if you want to get the history see my original post on the subject here
http://www.xt660.com/showthread.php?t=8394

I hope that helps your queries for what is not now really a major problem.