Given modern tax laws that penalize holding on to warehouse queen inventory, at maufacturer/wholesale/retail levels, I wouldn't lose sleep over it. Even for somewhat common sizes, in recent years I have been told a couple of times that I will have to come back Thursday, when the truck comes in. Like any other retail chain for consumers, they only stock what history shows they can sell quickly.
Of course, if you are talking real oddball stuff, like licensed 3rd-party repro Polyglas GT redline Bias Plies for your '69 'cuda show car, where they only dig out the molds and run a batch every five years, yeah, there might be cause for concern. 'NOS' is not a good thing for shelf-life parts.
aem sends...