Over time you should change up or add to the content of a hub. A hub isn't done when it's published - you can always edit it and improve it.
I'm forever seeing mistakes in my hubs - even hubs that I've looked at fifty times already - I still find things that need to be fixed or improved.
Add backlinks - there are "God only knows" how many websites out there that you can add a back link on without violating TOS
If you have questions about a site, and whether or not it's a bad site to link on - e mail a staff member personally and ask them about it. I do.