I have a personal caching class, which can be seen here ( based off WordPress' ):
http://pastie.org/988427

I recently learned about memcache and it said to memcache EVERYTHING:
http://highscalability.com/blog/2010/5/17/7-lessons-learned-while-building-reddit-to-270-million-page.html

My first thought was just to keep my class with the current functions and make it use memcache instead -- is there any downside to doing this?

The main difference I see is that memcache stays on with the server from page to page, while mine is for 1 page load. The problem I see arising, and this is with any system, is that they're dynamic. They change all the time. Whether its search results, visible products, etc. etc. If it's all cached, won't the create a problem?

Is there a way to handle this? Obviously if something is bringing back the same results everytime it would be cached, but that's why I was doing it on a per page load basis. I'm sure there is a way to handle this, or is the cache time usually set between 5 minutes and an hour?