Select tobacco, oftentimes in big bales or pallets, can be stored and used by a blending company for a long, long time. This has been talked about by the big blenders and blending houses. I know Sutliff has large stores of a variety of tobacco.
Depending on the source, it was believed that much of the Syrian Latakia last held in any meaningful amount in the 00's was originally grown and cured in some instances in the 70's.
It gets crazier with condiment type tobaccos, like perique. Imagine how many pounds of blended perique you can make with a single barrel, then imagine how much tobacco you can blend using that much perique.
The reality is that the pipe world is so small in the grand scheme of things.
My quick research showed that the United States alone produces at least about 282 MILLION pounds of tobacco a year. That was the LOWEST figure I could find.
The issue, which is commented upon very frequently, seems to be getting the quality of specific tobacco types to use for the purpose of pipe-making. Pipe tobacco just doesn't have the money or people to back an industry that supports directed cultivation, curing, and production that cigars and cigarettes do.