I think they will be fine for glue. The older they are the weaker the glue will be, of course. Personally, I think the hair should be removed. I soak my hides for a couple days in a hydrated lime solution (1lb for every 5 gal water). I like hydrated lime because it won't kill the soil where you dump it. The hair can be thrown into a compost pile.
The glue can be stored dry for a very long time (on the shelf). If mixed with water, it can be stored in the frig.