The cure was pricey and involved visits to the banya, strolling the grounds, a carefully prescribed exercise regime, and a recommended diet. It was therefore - this should come as no surprise - available only to the middle and upper classes. As many as 250 of them took the cure every year at Postnikov's establishment alone and its virtues won acclaim from Moscow to Paris.
There is a short essay about kumiss in the Illustrated Guide to the Volga River. It explains that kumiss could be found easily throughout the steppe provinces of Samara, Orenburg, and Ufa, but that there was a meaningful difference between proper healing establishments - few in number - and common "kumiss points," where living arrangements consisted of wagons. If one could bear the discomfort, the advantage of being in a more remote location was access to higher-quality kumiss from horses that grazed on the open steppe - the Illustrated Guide has few kind words for the quality of kumiss in the posher establishments.
This was a seasonal cure for sure: the time to take it was in the spring or early summer, when pastures yielded the best grass. But as word spread of the health benefits, both the temporality and the geography of kumiss cures expanded. A kumiss establishment opened in Crimea, and kumiss was bottled and sold throughout Russia and Europe to those who could not travel to the lower Volga or Black Sea coast.