I don't have a computerized machine, but when I purchased my machine so many years ago the Bernina dealer recommended that I get into the habit of unplugging my machine every time I quit sewing if it was going to be for an hour or more, and I never sew during a rain storm. When we have a rain storm here we usually have an electrical storm with it much of the time no rain, just an electrical storm.
I have always unplugged the power cord to the machine. I don't bother with unplugging the cord from the outlet. I know I can afford to replace a cord a lot cheaper than my machine. Now it is such a habit, that it's like turning a light on and off. When I stop sewing, I unplug, that way I know for sure there won't be any electrical surge or damage going to the machine.