I did a 6 month full time course, then a 4 year apprenticeship.
If you are working full time and don't know it in 2 years then you probably won't make it.
I didn't have the same resources as people have now - the internet wasn't invented when I was learning.
I'd say if you don't have the basics in 3 months, the intermediate stuff in 3 months and the advanced stuff in 6 months - it should all in all be a year.
And knowing software isn't going to be helpful when it comes to printing. You will need to know the difference and workings of litho/flexo/screen/digital/embroidery and how to setup for each. How and when to use spot colours, including neons/golds/silvers etc. how to setup spot uvs, keylines, and other things.
And that's just the basics of printing, there's trimming, folding, creep, spine widths, oversized folders, clothing printing, newspaper print, magazine print, high-end print, scanning, photography, photo manipulation... the list goes on.
Yes anyone can use software... but you really should do at least a year at a proper print place.