Hi, Thank you for this question. Updating your hub is a good idea for your hubscore and SEO. If you can find new information that your readers might find helpful definitely add that. Remember for SEO your going to target just one or two keywords per article and your content should be heavily relevant to that keyword.
A good way to find new information is to set up Google Alerts for G-Mail. For example if your hub is about a particular brand of digital camera then enter the brand name as an alert. Every time something new is mention anywhere on the web you'll find out via alerts and get the link in your email. This sends all the latest news and update to you instead of you having to search for it. And it's 100% relevant to your keyword.
Don't forget to get backlinks to your hub too. On-page optimization only tells google what your hub or article is about so they know which keywords it's relevant too. Off-page optimization if what informs Google how popular your article is. The more backlinks you have the more popular you must be and therefore you rank higher and higher.
Another issue with SEO is that search results are extremely personal right now. So it's important to include social share buttons on your articles or hubs, which they are, and make sure you have a goolge profile. Link to your hubs in your google profile. This tells google your the author. You should also have a google plus profile. Update your google profile with your hubs.
Google plus and SEO:
Google now has the option to show results from people in your circles on Google plus. If you take time to search and add people relevant to your articles and market, your articles and hubs have the opportunity show up when they search.
This is a giant opportunity to be relevant to people looking for the information you have to offer.
I hope this helps. Wish you the best of luck on Hub pages.