It is a glue and glues tend to lose grip when they dry out. I can imagine that the product will lose its effectiveness over time.
A little off-topic but still relevant: I use steam-a-seam and generally buy the packages because they are easier to store. However, I have recently noticed that there is a lot of transfer of the sticky stuff between the layers so I end up with sticky stuff everywhere. I can't remember having that problem with the interfacing bought by the yard.