I’ve heard of 4/5 months for a particularly high performing barista at a store that really needed a shift. Sometimes (even not counting being passed over) it is several years if there just isn’t need for a SS though. If no one is quitting or transfering out in your area or if there are transfers in, sometime there just isn’t a spot. Personally I would feel concerned about anyone being promoted before about one year though. I feel like that’s kind of the average minimum I was seeing (for a shift-quality barista) to be ready to step up comfortably. Some people can sink or swim before that, but, comfortably, a year. I was a barista for 3 years before stepping up (actively looking to step up after around the 2yr mark) and I felt like it gave me a lot of time to gather knowledge I wouldn’t otherwise have had.

Barista trainer doesn’t mean as much and is dependant on SM and if there are people to be trained and are there other trainers etc etc. I would say usually it was 8months+ as a ballpark but earlier is fine.