We've recently implemented a flipboard compliant feed using this module, it's really helpful.

I've set up a superfeedr hub and I can successfully ping the hub using the button on the admin page: admin/config/media/flipboardrss

What I'm confused about is that the hub never gets pinged unless you click that button.

I assume this is a planned feature. My understanding of PubSubHubbub is that you have to ping the hub when you have new content otherwise nothing happens.

I was thinking of implementing a simple hook_cron which calls flipboardrss_ping()

Or perhaps a hook_node_save() which calls flipboardrss_ping()

Flipboard is quite particular about the feed, and to get it to validate I had to add quite a few filters to my View, eg content type is one of X, has image, body length > Y, publish date no older than Z days, etc.

So all that logic is in the View, now ideally we would only ping the hub when that view has changed, but I don't think it matters if you ping the hub more often, so on node save would be pretty good, on cron less so but better than the current implementation of never pinging the hub.

Does this sound like a sensible approach?

I suppose you could do something fancy like save an MD5 Hash of the rendered view, and then only ping the hub if the new hash doesn't match the old hash.... but I'm pretty sure when you ping the hub it checks to see if your feed has changed anyway so I'm not sure that's really necessary.