Get out of my bed!

I love my dogs.  I love how soft Major is and how warm Kaiser is (this time of year at least), but they are total bed hogs.  About a year ago when we were having all the issues with the cat and her bladder stones, we couldn't expect the boys to sleep on their beds because, well, they were "dirty".  So while before they would jump on and off throughout the night, they both got in the habit of sleeping on our bed.  All night.  Every night. 

But now I want my space back!!!  So for a couple weeks we have been kicking them off and they aren't allowed on the bed at all.  But yesterday Brian came back to the bedroom after breakfast and they were snuggled down on our bed!  I need some tips for keeping them off ALL the time. 

I want a new duvet cover, but don't want to put something new on the bed until they learn to stay off.  Even when we are gone!