Im sure the burn-in is not a problem on this clock. You will only see it when its turned off, so just keep it on ;) Surely you wont notice if the digits are even 50% burned in. They will just shine less than when it was brand new.
Another much cooler option is to make the static stuff dynamic. Why not make the digits come to life? Make them jump,tilt,grow/shrink a bit. Make it stand out when the arms hit it. I could go on..