Last year it was very much like that for me, and this year is already showing signs it could be the same way. I will admit, last year was my first year on amazon after finally deciding to move away from ebay, and it was rather enlightening. From black friday to about December 18th, I spent most of my evenings packing and prepping stock. It was a lot of work, but very rewarding. Then about a week untill christmas, until about a week past new years, stock was still selling, but just not at the same rate. Then by mid january things were flat as a pancake, and have somewhat stayed that way throughout the summer. Finally, things are showing an uptick again...
I've learned, that from September 1st to January 7th, if one wants to create a rolling inventory stream on amazon, it's very possible, if you play your cards right and buy decent stuff throughout the year.
I always use the early part of september to blow out stuff that is either slacking, or no longer making any more gains, and use those to get my 25, then i'll start raising prices once i'm "in". This year, i'll wait until the second week of december to blow out all my items that I want to get at a premium, since that is the period when most of the prices tend to inflate, albeit temporarily until Christmas arrives.