Something funny about phenibut is that some can get a semi permanent tolerance to it. Someone mentioned 1fast400 (memories!) and that's around the time I discovered phenibut too.
I remember thinking "this is IT, I found my alcohol replacement". It was great. Then I kept ramping up the doses, and then it just didn't work anymore. I was so disappointed, but then again, years later I've heard plenty of stories about people trying to break a phenibut addiction.
These days I keep a small tub of f-phenibut around. It helps my wife when she has anxiety, and she doesn't abuse it. I myself find that if I absolutely must ensure that I get a great night's sleep, it does the trick. Couple times a month, if that.
I'm still going to keep on plugging CBDV flower. Great anxiety relief and no downside, and perfectly legal.