the 4 year time lag isn't that much in academic circles, I've seen papers in some fields published abroad picked up here only after a 10 year time lag for example.

How does that happen? It's not like people are reading foreign journals at a 10 year lag. Maybe they're reading them in real time and after 10 years of seeing the paper cited repeatedly, they take it seriously. More likely, they're just not reading the foreign journals, but one day they went to a foreign conference and met the author or a protege - not going to happen with interstellar distances.