It depends on the topic and content of your hub. If your hub contains movie reviews, poems, philosophies of life, then its better to set it and forget it.
On the other hand, if your hubs are based on dynamic topics like latest fashion trends, latest operating system, best movie rippers, then it is better to regularly update them. After all, you can't expect people to read a 15 year old article on Windows 97. They would rather be searching an article on windows 7.
You can also update them for improving them and adding some points, which you had forgotten earlier.