I'm still using out of the first liter that I ever bought. I haven't been mixing that long and never used to keep much on hand and used to buy smaller quantities. I don't remember how old it is but bought it long before I had a freezer to put my nic in. I bottled it in 100ml bottles and got one out the other day and it was kind of an amber color. Fairly dark but it was most likely dark when I put it in the freezer. It sat in my basement cabinet for quite some time. I have a couple of clear bottles that I bottled last year and put in the freezer right away and it's as clear as water. It's actually surprising how long a liter of nic lasts.
Good luck. Try to stay safe.
The 250ml bottle I took out of the freezer was dated 2013 and clear as a bell.