Even when they take a beating, finished leather can last for hundreds of years. So, age isn't necessarily the cause of stiff leather items. But without proper care, even a high-quality full-grain ...
Shelterrific highlighted this awesomeness: the WD-40 website lists more than 2,000 uses for the wondergrease! My favorites on a quick perusal are "Unclogs shower heads" and "Softens stiff leather ...