Websites can easily fall behind if we don't keep them fresh, modern and up to date with the current trends and your content can become out of date really quickly. Websites are like a shop window for your company so it's really important to make sure it's looking and feeling its best.
If you had your website built a while back and you think it still works for you, I would say you need to reconsider. It worked great back then when you first planned it all out, but you've changed, your customers have probably changed since then, and your website might not fit everybody's needs anymore.
Evaluation
It's really important to revisit how your website is working for you on a regular basis, every 4 months or so ask yourself if it is still meeting your customers' needs as well as your own. Follow these simple questions to see if it's still working:
Who are my customers?
Do they still match the same criteria as they did four months ago? If not you probably want to update some of the pages to reflect how you deal with your customers.
Does the content still match our products?
As time moves on your products will evolve, and as they do your website should always describe them perfectly. Your products and services have probably evolved because you've improved them and so there is potential here to gain more customers from having up to date content. It also ensures you're staying as competitive as you can be in your market.
Is the website easy to follow/navigate?
Navigation is really important on a website, and 4 months of editing and changing your content might have left the structure in a hard to follow state. Reflect here by looking at the homepage and ensuring you can easily find everything that you want your customers to see. If a really important piece of content takes you over 2 clicks to find it's likely the person you want to see that page won't find it. Draw out a simple navigation diagram to ensure every page can be found easily.
What do you want a potential customer to do?
If a potential customer lands on your website, either through a search or if they're reading some of your content, typically you want them to then become your client. If it's not obvious how you want them to proceed after reading the content, they will usually just leave. If you want them to become a customer you must tell them how. Your call to actions have to be obvious.
Does it still look good?
Your website has to be pleasing to look at, but it also must be easy to use. UX methods are changing constantly and designs can quickly look outdated. If you haven't done a review of your websites design for some time it might be worth thinking about.
I hope this list gives you a good start in looking at your website and ensuring it is constantly looking good, saying the right things and giving you and your customers exactly what they need. Things can quickly get out of hand so remember to evaluate often, usually evaluating every few months can prevent you from having to rebuild your website and do a complete new restructure every one or two years.