Some types of vulcanized rubber, like those in tires, can take both heat and moisture. But I've not had any tires for 25 years, so I don't know for sure if rubber can last that long. But, people pass "little red wagon" toys, with tires, down from one generation to the next.
Some types of foam too - I've had kayaks that I kept outside, using closed cell foam to reinforce structure and/or improve fit, sometimes for 20 - 30 years. They would get wet (kayaks do), and when it was sunny and hot, they would get hot. In one case, a black carbon/kevlar/epoxy composite boat, it sometimes got hot enough to smoke in the sun. Nothing ever turned to goo, or suffered obvious damage, aside from color fade. I've also had sponges (also used for kayaking) that have lasted since 1980 or 1981 - 33 or 34 years. Though I suppose that the materials used for boats are deliberately chosen to be very tolerant of weather...
People ship skates all over the world when traveling, or when buying new, so skates must be able to take the usual conditions of shipping pretty well. And if the o.p. carries the boots in carry-on luggage, they can't get too hot.
Maybe buying them in the U.S. will also save on import and export tariffs - if they are made in the U.S. Incidentally I once bought a kayak in Canada. After I declared it at the border, and filled out appropriate paperwork, the Canadian government refunded me the sales taxes, which are very high in Canada. (They did insist on inspecting the boat, which wasted some time.) If that is still true, and applies to skates, and the skates are made in Canada, the same cost saving may apply - if the o.p. lives near Canada.
(OTOH, Edea skates are from Italy.)
The comments in the other thread, about using a fitter who is very good at fitting, rather than worrying too much about their location, makes a lot of sense too.