I wouldn't say they die after one marathon. Mine have 135 mi on them, including one marathon and a couple shorter races, and they still feel great. At 25 lbs. heavier than you I probably punish them a little more under ordinary use. They show more wear than I'd like, with a touch of slightly ragged bare foam showing on the outer corners of the heel, plus the characteristic wrinkles/apparent crushing of the midsole that you just have to get used to. The shoe has a very thin rubbery casing like a sausage around the ZoomX that abrades easily, and they might look pretty ratty around the edges after a run on limestone. Guessing this is one reason they went with a protective cover of React on the sides and beneath the ZoomX on the Pegasus Turbo.
Nike of course wants you to buy a pair of Zoom Fly for training and Vaporfly for racing. I did that but never liked the Fly too well. Some people say they have a fast feel but that was not my experience. They lasted ok, 375 miles, but I was more than ready to let them go at 300. The Vaporfly I will definitely buy again.