There's a lot of knowledge in this room on nic storage, and I appreciate the opportunity to learn from it.
Back when I first started DIY, I bottled my nic into 4oz. amber polycone capped bottles, but only with 100ml in each of them. Not sure why I did it that way, but I did. It's been almost four years now, and even though there's quite a bit of head space in there, I don't see much if any discoloration of the nic itself when I take a new bottle out to use it. It's consistently stored at -10F, in the amber bottles, in a cardboard box, in the freezer.
The newer stuff I've purchased for the long haul is all bottled and stored the same way, only now it has as little headspace as possible. I'm feeling better about that stuff lasting me 20-30 years as I've budgeted for.
I do tend to wrap caps of full bottles with white electrical tape. It's easy to write on and let's me know that I've never opened that bottle for anything. I think it might just make me feel better about the storage process, however misguided that may be.