Depends on how long you mean when you say by the time you're ready to pull them out. Some people go through their pairs pretty quickly so you could mean anywhere from 2-3 years to 12-13 years. Other points to consider are the lack of knowledge about the longevity of IVs produced from '04 until now (2004 pairs might start crumbling in 2017, who knows) and the lack of knowledge of JB possibly using different materials in the midsole. As far as crumbling, I've seen only the 4s that were released in 1999 crumble. Idk if that issue has made it's way to 04-06 releases because I don't have any. They probably have tho considering folks DMP VIs are falling apart (recently happened to fat joe who claimed he kept them DS). Hopefully JBs been using new materials in the midsoles after the 1999s to combat the crumbling but until we find out for sure you should still go ahead and double if you really like a particular release. This years Oreos were pretty solid. I liked the materials used on the upper and I noticed that after 20+ wears since initial release up till now, there isn't a single crack on my Oreo IVs midsoles. My 2012 bred IVs tho.. don't get me started
If you do double and want to keep your 'on ice pair' in existence longer, fret not for there are now methods and ways of going about to prolong the life of your 'on ice' shoes before the dreaded crumbling. Even on shoes like 4s with air in the heel, we now know that if you lightly wear your stored kicks once in a while, like every few months or so, your shoes won't crumble as fast. I'm guessing the added pressure from your body weight brings life to the polyurethane midsole that, if left stored away without that weight from your body applied to it every now and again, would dry out and crumble. There are members here that can still wear 1999 pairs and other older releases without worrying about crumbling because they've always worn them since they released, some sparingly and others religiously. But in the same breath there are many other members who have kept their shoes stored and in true deadstock condition that had their pairs separate, crumble, and fall apart on very first wear. This method ultimately won't stop them from crumbling completely but it will definitely buy you some time. Overall what can be said is that the best way to preserve your jordan sneakers, your pieces of sports and pop culture history that you want to keep mint condition for as long as possible to continue enjoying them in their pristine, nostalgic condition, is to simply wear them; a practice many collectors don't want to do. Ironic.
Sorry for the paragraphs