This is why I'm so fond of TPA/TFA. Things can very well change up a little, but as soon as I give my newly mixed flavor a good shake, it tastes great(at least I assume it does..since I'm full of myself), and that's how it will remain..
The only negative I see with TFA is that majority of their flavors contain PG.
Also....are you only using the tangerine flavoring? I typically use at least 4 flavors in the most basic flavors I mix.