We had purchased ours to use for our month long vacation last summer after reading about them here on FRF. Used it while plugged in at home for a few weeks with no issues.
The week before our trip, DW and I decided to take the MH to a campground about an hour away for a final test of all systems before our long trip. Plugged in the PD 30 EMS and received an error code. After getting the campground manger to get his electrician to check the power at the post we plugged in and all was fine. Called the Progressive the next morning, gave them the code # (250) and they said that water had gotten into the box somehow and that I could send it in and they would replace it. I explained that we were leaving in three days for a month and they said no problem. They over nighted a new one to me and said I could send the old one back if I had time or I could do it when I returned from my trip. Got the new one and had not one problem with it since.
Also, we did get a very bad thunderstorm with a lot of lightning one night in Montana and power dipped several times. EMS shut down and stayed off for about 10 minutes. Came back on and everything worked just fine. 2 neighbors lost their televisions and I heard another camper later talking about their microwave was not working well since the storm.
Like several have said, "it's just insurance." It's up to you to decide.