In the entire time I have been on the Web (since 1996), I have only redesigned my Web site twice. Once was when I first designed my original Web site, and once in 1998. Since then, a LOT has happened in my life (PhD completed, got married, became an uncle, started a few organisations, etc etc etc).
In the meantime, so much of the web has developed. When the original web page was first developed, it predated frames and tables, PHP and mod_perl. The funny thing is that my web site hasn't changed much in 6 years.