Bandit is a lab Sheppard mix and will be 16 shortly.  He has arthritis in his hind legs which now limits his mobility. He loves his new bed.  I have looked for proper supportive beds before but they have all been disappointing, I am happy to report that I was not disappointed with the level of support.  He sleeps the entire night without needing to move around. Only thing is the large is just a little small for him as he needs to be laying diagonal when fully stretched out. 
Our younger dog will probably be getting a bed upgrade now.