I get asked this question often. I have found that usually it is by CEO’s or webmasters that have not updated their site in the last 5-7 years. Some might say “if it is not broken, then don’t fix it” but I have to disagree. We are living in a digital age where there is no brand loyalty, there is only what is the best and how can it help me today mentality. I make no bones about it that I use Optimizly for my A/B testing or multivariant testing. I do it, I tell others to do it as well. Just watch out for their sales people, they will always try to sell you on the gold plan. Also if you site is not getting enough traffic, it will not help to test. You need to have a large enough sample group to test from.
When you dig into what your site and your competitors are doing then you need to keep up with the Jones so to speak. If you are a city website, you can get away with updating the site every 5-10 years. If you are a publishing or an E-commerce site you have to keep current. You will get passed by your competitors. Your competitors are looking at you if you are first and they are gunning for you.
You should be updating your site every 2-3 years. Think of your phone, you usually get a new phone every 2 years, why not a refreshed website. A stale and outdated website can hurt you. You visit websites all of the time, you know what you like and what you do not like yourself. If you were to visit your site today for the first time could you say that your site was fresh and engaging? Helping the user? Helping the Search Engines to understand what your site is and is about?
If you have a stale site, re-invest some money and re-work your site. I once worked on a site that had not refreshed since 2005 and it took them till June 2014 to re-work the site. Nine years is just too long and it is one of the reasons I left there. Taking too long to re-build a website is just sad. I know it is a cost effort, you have to hire someone or outsource to a team. But in the end you have to re-design and stay ahead of your competitors.