I had to stop by the local grocery store this morning. The same store that I have patronized for the last twenty odd years. The parent company has decided that the store needs a facelift, and I agree. The problem is that now I cannot find anything! Over the years I have come to know this store like the back of my hand. Today the toothpaste was in a new aisle, the peanut butter was no longer grouped with the jelly and the frozen food section was completely backwards!
What does this have to do with websites?
Every website needs to be freshened and updated on a continual basis. Frequent visitors to the site will begin to skim over it quickly if the information and format never change. So even if you add a new comment here and there they will miss it. Every so often move things around, reword the page so that it stills imparts the message that you wish but looks slightly different.
Changing the website will also make it appear higher in search engines as they are designed to detect static pages and rank them lower.
Back to the grocery store analogy. The problem with some websites is that they make overhauls in such a drastic manner as to make a frequent visitor feel as though they have never seen the site before. You should take the effort to guide your visitors through the redo of your site. Perhaps send out an email to your list that bullet points the changes to your site. Phase changes in over time so that it is not a flash-cut. Announce the changes on your home page.
The end result should be a freshened appearance with none of the shock.