Don’t count on Google and Yahoo! to keep sending traffic your way if your site has gone dormant. While it’s true that once a page gets listed, you’ll have a hard time getting delisted, a lack of updates can certainly diminish your results.
Part of the search engines’ algorithm is the use of the freshness of a website to help rank your sites content in the search results. Now, it won’t affect it as much as your linkage, but it does make a difference.
The more you write, the higher you’ll rank for freshness and the higher you’ll rank period. The concept is the key one in why blogs have such a high rank in most of the search engines. The natural freshness of a new post once or twice a day or even just once or twice a week combined with the excellent nature of blog interlinking make them the darlings of the search engine algorithms.
So, if you have a hot page that gets a lot of hits from the search engines, the best possible way to make sure that you keep that traffic up is to continue to create new content. Well, that and continuing to write on the same content as the page that the search engines hit. But that’s another post.