How often are you updating your site and marketing materials? If you're not thinking about updating your website and its imagery, it should be something on your to-do list. Most times it's your website that art buyers and photo editors peruse through to get a sense of your work and your clients before your book is ever called in or a conversation is had about a project. If it's not consistently updated, there may be a a possibility these people will pass over you.
It's so worth taking the time to add new projects/images that you've been working on and replace some of the older images... or keep the older ones if you love them but make sure the flow works well.
Does the layout of the site feel dated? If so, update that too.
These are the bells and whistles that attract people to hire you for jobs. While you might not be a designer by trade, photographers/illustrators are creative people and as a buyer I would this creativity transcends through your imagery and to your marketing material. It doesn't have to be changed every three months but update imagery when you can, definitely at least once a year. And when you have a new project or when you update this imagery send out some promos/newsletters to drive traffic to your site.
I just received a simple e-promo newsletter layout from Sharpe + Associates that included one new image from a recent project for each of their photographers. No lengthy explanation just brand new imagery to click on that sent me to the site and the blog for more news.
Updating your website and its imagery is a smart way to keep people interested and consistently drive traffic to your work.