On today’s web, is a website ever a once-and-done event?
In traditional web design, you start with a website (see chart below) based on the assumption that “it will work” to achieve whatever smart goals you've set. After a year and a half to two years, you see that performance is dwindling and you embark on a 3-month redesign. You gain impact and the site works for another one and a half to two years before performance falls flat again, and you have to repeat the process.
The chart below shows that gains occur abruptly and fall flat quickly.