We allocated around 1.5yrs to 2yrs for this process. There's no rigid answer for "how long does this whole process gonna take", if you are lucky (and have a simple case with no redflags or whatsoever idk), your case probably will move faster than others but generally speaking, from what I have seen at the "popular" tracking website, they have around 2.5k ~ 3k cases approval flow per month since earlier this year (last year was very efficient but hell with new policy, reduced workforce, I am glad they still going at a steady rate lol). Also the timeline is very variable and heavily depending on things like are they gonna ask for RFE, how long does it take from NVC to your Consulate, wait time to setup interview, and so on...
For example, in Canada, Montreal is the only place that do K1 visa which could create a huge back logs so yeah, it is hard to predict, no certain answers and the only thing you can do is leave it there and checking-in regularly. It is a lengthy process (and stressful as well) but checking-in everyday will just gonna make it feel so long. So find something to do, plan something exciting to look forward to it, and breathe, you will get there.