Either way I know it can be worked around, my point is that it’s important to inform less knowledgeable users that installing a beta could cause them to scratch their head six months from now. And experienced testers tend to forget about mentioning it to users because they already have the extension and/or don’t mind using a beta all the time.

IMHO there should be some kind of checkbox to unsubscribe from beta updates. Very often the situation is that you really want some new features from the newest version, so you’re willing to temporarily put up with instability to access the new features. You’re happy with your brand new beta Firefox, then it updates to the final version and you’re still happy. Three months later, a new minor beta appears and you’re forced to use it because you didn’t think of disabling the beta update channel. But this time, there is no reward for the instability of beta versions: there are no new features that would make your life easier, you just risk losing data without any benefit. Not to mention that when you installed the beta 6 months ago, you were willing to put up with data loss or spend time frequently backing up your profile but nowadays maybe you can’t afford to lose data.