Like most we leave ours connected, but we do put the front and rear jacks out to stabilize the unit. We never put the slides out unless we are level, no need to temp Murphy's Law.
C-Bears good point on the live wire and better suggestion with respect to tennis ball modification.
I had purchased at one time tow red caps one that fit in the TV 7 prong outlet to keep dirt/salt from coming in in the winter and the other fit on the end of the umbilical cord. Such a popular item that I managed to lose two sets and have not seen anymore. Cut tennis ball would likely be much cheaper!
GPG