I have eight cornsnakes, and I very rarely see any of them moving about. One snake seems to stay in the same spot every time I look in his viv, but now and again I 'catch' him out. All my snakes are in a room just off of my kitchen, and I can glance in the doorway with the light out and catch them having a little stretch, but if your corns are in the same room as you live then more than likely your snake will hide until everyone has gone to bed.
If you really want to see your snake excercising firstly find a torch, then switch all the lights off, close all doors, and turn all tv's off and just sit. The snake thinks 'goody, they've gone to bed, time for fun', and they should come out, but this could take a while so be patient. After a while switch the torch on and have a peek, that is if you dont fall asleep first, hence its morning and you have missed your snake roming about because the lights are back on!
Good luck!