I also have planted pears in MN, near Fergus Falls, and have had similar mixed experience. I planted a few varieties 3 years ago and the ones I have remaining are Ure, Early Gold, Patten, and a hybrid from Morse Nursery. I lost some this winter including Parker, Luscious, and a Keiffer. I have had pears on my Ure but only the second year. I am not fully throwing in the towel, but am doing similar to Sandbur and starting to pivot more toward apple-crabs and the like. Still hoping the pear trees I have remaining can stick around and at some point set some more fruit, but I am tempering my expectations accordingly.