Refreshing existing hubs is a good habit to make, but adding new hubs is very important. I am not a fan of the 100 hubs in 30 days challenge as it is diluting many writers scores because much of our score is based on page views. Most people are so busy writing; that no one is reading. Which, to me is like spending all your time stocking shelves with product that no one is coming in the store to see much less purchase.
However, I realize that many people think the writing challenge is going to help them. I see that HUB is getting new content, yet no one is benefiting that much right now that I can tell, so, adding content for the sake of content is not necessarily good.
Think about what you want to write about, and what someone else would want to read, and write with that in mind, using keywords throughout your article.
I hope our readers return, and perhaps I am wrong about the hub challenge, but in my opinion, it's never a good idea to flood content on any site, but to add good content regularly.
Certainly for those who have not participated, it's almost as though we do not exist, and I did not expect that penalty, frankly.
So, perhaps I've gotten off topic, but I just want to stress that adding good hubs is important, but give the hubs you write time to cook...=)) good luck!!!