There are some cars that go through rear tires relatively quickly. Mostly these are RWD powerful mid and rear engine things like the Porsche 911, Cayman and Boxster, the Audi R8, Lambos, (old) Acura NSXs, Ferraris, etc, though I have heard bitching and moaning about Porsche Cayenne rear tire wear. In these cases 8000 miles street miles on the rears is considered terrible, and 10K-15K is more typical. On our Cayman and Boxster we usually got about 12-15K on the rears, and twice that on the fronts. That's typical for street-driven 911s too. Even the cars I've heard about that come with Michelin Sport Cups from the factory (like some Corvettes), which have very little tread, see about 7000 miles before they need replacing. So 2500 miles is very suspect, though I would guess tire manufacturers see it all and hear it all.
I've never heard of storage conditions or cold weather driving severely impacting the life of summer tires. I use summer-only tires on two cars year-round in a locale where it gets quite cold, and I've never noticed a difference. The problem with summer tires and cold conditions is traction, and in that respect there can be a significant degradation in performance. Some max-performance summer tires get a little loose on freeway ramps and tight corners when they're cold, and you have to be careful lest your rear suddenly becomes your front.
