I find that if I buy them from oct-jan/feb, they store very well in my basement. I just leave 'em there and I can keep them for weeks...I think I accidently left one sitting for a month and it was fine.
THe spring/summer crop must be different because I can't keep 'em for more than a few days--if I'm lucky!
I can't imagine it is a different hybrid but maybe the rate of growth and water content is different during different seasons, which would affect the storage capabilities. Just my 2cents. I'm no gardening/storage expert.
Thoreau said, 'A man is rich in proportion to the things he can leave alone.'