A bubbly burping boy!

Last week two precious, adorable, little boys came to live with my dh and I. The oldest (3 1/2 yrs old) loves to burp ALL of the time. We have taught him how to cover his mouth and how to say excuse me, but I am stumped as to how to get him to realize there is a time and a place for things like that. I don't want to tell him to stop burping completely as sometimes he is going to have to do that, however he seems to enjoy burping just for fun. Is this a toddler issue? Is it a boy issue? How can I set boundaries on his burping? At this age does he really understand that it's rude to burp whenever he wants? I know we are still in the "honeymoon" phase and this seems to be where he is testing the most, so any suggestions would be greatly appreciated. Thank you! Claschober :)