I often hear about how important it is to go back to hubs in order to tweek them.
Tweeking allows you to look at the stats section in your hub to check how it is performing.
I have tweeked my top 3 hubs in terms of page views and they are quickly getting more hits.
Adding key words from research is definitely the best time investment you can make.
Just tidying up and adding dividers makes a hub look that bit better than when you first published it.
If time allows do a few hubs per week and tell me of your results as I would love to hear.