They run periodic sales through the website for a defined time frame. When that time is up, it's pulled. The stacks work in a similar way, except with those you have to also take into account stock and discontinuation. It also allows retailers a chance to pick up and carry the product line as well (no company likes competing with themselves at a retailers shop). No worries, there will be other stacks and sales through the TN website in the future I'm sure. If you had a specific stack and pricing in mind, it could never hurt to hit them up through their CS email to ask about it. I'd give it a shot and mention the stack you were interested in as well as the defined price point it had. Never can tell, they may work with you on it....