Clearly the only advice Jim needs is to keep on keeping on. Or just do it. Or some other myriad of annoyingly vague things that accumulate to him being told not to stop.
He doesn't even need that. In fact, telling him that is counterproductive; after hundreds of people have told you to do a thing, even if it's a good idea, it gets
really old. Besides, it's pretty much a given that he already knows it.
In short, if you feel the need to tell him to do something, don't. Doesn't matter how well-intentioned the advice is; I can guarantee you he's heard it over and over and over and over and over... you get the picture. If you just
have to tell him something, say how much you've enjoyed reading his stuff. That's good enough, and there's no way it can come across wrong or pushy or passive-aggressive.