I slept with mine on until the OS said it was OK to do without them. They are mainly for protection if you toss and turn. But I know how hard it is with both legs being in braces. It is really uncomfortable. Until such a time as I could roll over in bed, I slept on my back also, but then started sleeping on my side with my braces on and a pillow between the legs and especially the locking mechanisms. I also knew that if I needed to get up in the middle of the night, I did not have to worry about putting them on.
But, I guess it is up to you. Just take care of your knees.
Tom