I don't know why I had such a hard time finding a citation for this. A couple years ago I had read that the piperine content of pepper increases during storage. I had used this as an example of why degradation isn't necessarily a bad thing, but rather it depends on what it is being degraded to.

I was beginning to question whether this was a real thing. Now that I wasn't looking for it, here I find it. I was actually searching for proper storage of piperine. That is, how should I store it if I buy large quantities.