I take the stuff in much lower concentrations, 1g/day divided into 2 500mg doses. I will do this for 4 or 5 days and then cycle with 1g of Taurine, 1g L-Tryptophan, and 1g L-Theanine 2x/day (2g each/day). I'll stay on the amino acid cycle for 8-10 days. I'll also use honokiol and picamilon sporadically. Honokiol is an amazing anxiolytic, without observed withdrawal/rebound effects in mice or humans. In fact in one study, which I'm too lazy to find an abstract for, showed a tapering of effects over a week after abstaining (mice), while the control group given diazepam went into immediate withdrawals. It's also good for the liver and an antitumorigenic. This stuff is expensive. That's the only problem.
I've never really pushed the limits with Phenibut, I doubt I've ever taken more than 1.5g in a dose. It seems to work just fine in this cycle. I think this stuff is really dose dependent and isn't really suited for recreational usage. I also take 100mg/day lamotrigine(lamictal), 2mg/day clonazepam, and 300mg/day bupropion(welbutrin). I'm trying to slowly taper off the clonazepam. I was able to drop from 3mg/day to 2mg/day over night when I started this cycle. I figure if I cycle anxiolytic cocktails while tapering I should be able to do this painlessly. I just don't like being on benzos, I've been on 'em for 2 years and I don't want any long term affects. I probably will continue to use other anxiolytics in a cycled fashion in the long run though.
That being said, I think recreationally, phenibut does have a place as a potentator, that adds unique effects of it's own, for other fun substances. It's nice when combined with Kratom, various opioids, moderate amounts of alcohol. I'm talking about a 1g or less dose. I know I just advocated mixing depressants. Be careful. You don't want to stop breathing. One probably shouldn't have more than 5 drinks after taking a gram, or go blowing 45mg of oxy with no tolerance. Hehe.