I haven't been able to get good pumpkins here, except before and after Halloween, and those are not great IMO. I asked someone coming over from South Africa to bring me some pumpkin seeds, I hope he does! If so I will give this a shot once I have a crop grown.
I am putting in many pumpkin and butternut plants this year. I love winter squashes, and I have found that butternut stores pretty well into January in my basement. The dehydrated pumpkin sounds like a great idea. I love squash/pumpkin soup and it would be perfect!
I didn't plant any pumpkins/winter squash last year, but the year before I grew Pennsylvania Dutch Crookneck, and they kept in the cool room (back bedroom) from Oct until this past winter when the last one was finally eaten. So a full year.
This year I'm planting more Penn Dutch as well as a few other heirloom winter varieties, and have young plants ready and waiting to go into the garden as soon as it's dry enough.
I've never planted pumpkins but I have done well with butternut squash. Much bigger than the ones in the store. Any squash or pumpkin probably will last much longer than the ones in the grocery store. They have been jostled around too much.
I bought a butternut squash ages ago when I had a craving for some. The craving promptly disappeared, so I put the squash in the kitchen and am keeping an eye on it to see how long it takes so show signs of "eat me, or.." So far it's looking fine. Storing vegetables in this wet climate is interesting. Everything either goes mouldy fast or tries to grow. I've never seen a head of cabbage grow before I noticed these leaves suddenly show up behind it on the shelf one day.. Oops.