Lifespan of a website is normally less than 5 years. I see many sites that are 10 years old and have not been updated.
Old Sites Give Bad Impression to Google and Public
It tells Google and whoever is searching for your company that you are not interested enough to keep it up to date.
You Website’s Code
The internet changes often, causing the code required to run an efficient site also changes. Example would be the PHP required to run the Database that WordPress needs. As of this writing, I have sites that are running Version 5.3.6. The world is now up to 7.4. Version 5.3.6 is going to be eliminated. When that happens, all those sites that still have it will go down…yes, DOWN!
Why Should I Add New Content To My Website?
Think of it, again, as trying to let Google and the public know that you care enough to keep it fresh. How many times have you gone to the store and found that the products have been moved around. Why is that? To make you LOOK for what you want…and in the meantime, you’ll buy something you didn’t intend to. Marketing 101.