Google looks down on websites that aren't updated on a regular basis.
Updating your site is extremely important. You want to keep things up to snuff, current and relevant as you want your visitors to know it`s up and running! I hate looking at sites that look like they haven`t been updated for OVER a year. If the tumble weeds blow through it easily, and that`s not the way a serious site should be seen from a visitor perspective.
When you have a website, you have to look at it from the point of view of having your own business. If you had your own business, locally (a store), would you keep your products up to date? Inform customers of any changes to your services? You have to stay current.
If not, then how are you customers going to view you as a business owner?
Updating your sites then pinging, even once a month is sufficient enough