The project of learning to critically read the primary literature is going pretty well so far. I'd like to add another stage to the four stages I mentioned:
5. Selectivity. At this point you become able to read "the literature" as a whole, not just individual papers. You can make a good guess about what's important without having to read everything in excruciating detail.
I'll also note that the stages overlap quite a bit. I'm still mostly in Credulity, but there are some papers I can actually criticize, and some I still fail to understand.