I own a Progressive 50 Amp portable. I never plug in without out. Not only do Progressives protect against high power, it also cuts off for low power. It will automatically reset and allow power in once the issue has resolved as power fluctuations will. Power can damage electronics and appliances over the long haul and power surges can kill them immediately. Modern units are chock full of sensitive electronics.
Good management units are costly but one power surge will cost many times more with the losses and inconvenience. Every year in our travels, we hit at least two campgrounds where it cuts off power. Worth it.
I had a unit fail because I left it uncovered in a NW downpour and moisture got inside. Unit says moisture resistant............ Called Progressive, sent it in and they repaired for free and sent back. I am a happy customer for as long as I can RV.