It's hard to know what to value a property today for insurance purposes. I know people who had got prices earlier in the year for renovations but the builders couldn't fit them in unless they paid half the money upfront so he could buy timber, insulation, and plaster product, etc. They didn't want to do this and their quotation is out the window now so to speak. In one instance it was originally €140k and that is now €200k. If he wants to go ahead with it, he pays half upfront again but he will not see it started until after Xmas. Yes, prices have gone up and some products by a lot, but there's a fair hike in builders prices on top of that.
With the above price increases, I personally wouldn't be taking out an insurance policy for 3 years duration, regardless of if the insurance company allows you to increase the property value or not.