I did a site back in 2000 for a local health related business (just a brochure site, no e-commerce), and updated it in 2002 (mostly I think I just added more table cell graphics

). I suggested back in 2005 that it needed redesigning, but they never responded. An opportunity arose recently to suggest it again, and now it seems they are more interested. Its a site that could be good, but is currentlt dragging my portfolio down.

In drawing up proposals, i got to thinking about website years, you know, like dog years but for site designs. It seems to me that 1 human year is about 20 site years: after 1 year (20 site years) the site is leaving adolescence, after 2 (40 site years) it's hitting a mid-life crisis, and after 4 years (80 site years) it's in its old age.
Is there a better rule of thumb anywhere?