Very well pointed out. Sharing an important topic with a community IS the "first and foremost" advantage of cross-posting.

I was however excited by the possibility to monetize older-than-7-days content, in a non-abusive way obviously.

Update: The manner I see best fit is to cross-post worthy content of other authors, not your own, and with consideration for the intended audience and its rules. Personally I'm a very light resteemer. If no other rules would apply, I would guide by similar principles when cross-posting as when resteeming.