Lots and lots and lots (hundreds of thousands) of people in Russia have been officially infected and diagnosed twice. Many Russian docs who worked with Covid patients have already been sick three times.
And yes, most of the time they say it's 3-5 months for asymptomatic cases and 9 months and more for severe symptomatic.
It appears that Russia has a different distribution of coronavirus strains than the rest of Europe [0], but the strains in Russia are certainly found elsewhere. If hundreds of thousands of Russians were re-infected this would be observed elsewhere and documented.
The closest thing I can find to reporting on this matter is here [1]. The Siberian Times does not appear to be a reputable news source [2], and its claims do not match the magnitude of those above. It reports that Russia’s chief sanitary doctor Anna Popova said, "in Russia there was not a single confirmed case of coronavirus reinfection." Furthermore, the doctor on the other side of this disagreement has "heard about other cases [of re-infection] elsewhere in Russia from colleagues" (and claims to have been re-infected).
This is not "lots and lots (hundreds of thousands)"...
There is evidence of re-infections in the scientific literature, but they are exceedingly rare (tens of people worldwide). Long-term immunity will have to be measured, especially in light of new variants, but current evidence points in that direction.
As of October, "The confirmed examples worldwide [of re-infections] could possibly be counted on your fingers" [0].
Immune memory cells, which are more potent than antibodies, persist for longer than 6 months [1].
We don't have data to support 2 years of immunity, but current evidence is pointing at it being long-lasting [2].
[0] https://blogs.sciencemag.org/pipeline/archives/2020/10/14/im... [1] https://www.nature.com/articles/s41586-021-03207-w [2] https://twitter.com/EricTopol/status/1349898485756162048