This is common knowledge in the drugs community and harm reduction sources frequently quote the 3 month thing, although I'm not sure where it originally came from.
Ymmv!
It absolutely does screw with some people's mood for the worse, but definitely not everyone, or even most people. I do think for people predisposed to depression and anxiety, heavy usage can be a bad triggering or worsening factor.
I don't speak for anyone else but it does not match my experience and FWIW I've been taking it once a week for ~4.5 years.
(Explanation; I consider that dose and rate as a definite abuse of it, not sensible use, but the past few years have been just terrible god knows how I would have coped without it. I'm improving now and started cutting down, and looking forward to going out without any drugs, even alcohol).
Until people come out with some real data I would stick with the cautious approach.