When it comes to Content marketing , we always focus on creating a new content.. Many webmaster & business owners have wasted ample of money in creating new content , but have either succeeded or failed in creating an impression..
I would suggest to go for 60:40 ratio , 60% invest on new content but 40% on updating the old one.
We can take some learning from this Wikipedia example and update our older content present on some of our top landing pages. This would be extremely effective not only to the business but for the end user as well. Search engines highly value content that benefits the end user and this strategy of updating the older content might work really well.