Leave the slug always powered on.
It only uses 7 watts so there is little electrical cost. When pc's cost $4000 in the '90's you would leave them always on as the cost of electricity was less than the cost of replacing the pc. Now, with pc's only a few hundred dollars and using over 100 watts in many cases it makes sense to turn them off when not used.
When I buy a new electrical device (tv,etc.) I will turn it on/off(unplug) daily+ for a month+ to "burn" it in and see if there are infant failures on components before the return/warranty expires.
What is hard on components is the heating up and cooling down of these devices. This is why most failures occur to electrical components.
I used to work at a company where we would do testing and burn-in testing of chips and most component failures occur right away and then level off over time. Burning in components involves heating/cooling/ humidity/ no humidity to components to simulate years of stress on the components.