Who are the current sources?
Nicotine Giant (1 who still has it) has
very good 100mg/mL nic base, IMO, based on my experience with it...back when their name was RTS Vapes. I bought 3L of it several years ago. Opened and started using 1, and just poked the other 2L back in their shipping box, and put it in a closet in the coolest part of my house. Had intended to later decant them into smaller glass bottles and put them in my freezer. Well, I forgot I'd put them there until 2 years later when I found them. I thought OH GEEZ...they'll be worthless now! But, I was amazed that they were both STILL fine...weren't discolored, had no odor, and were as good as the first Liter I'd opened.