Chrome runs a new process for each tab i think. I remember reading that somewhere.
The thing is to though is you should be able to have chrome remember the tabs that where open, so when you reboot and open chrome it will reopen the tabs.
I have to admit, in 16 years in computers (I'm 32) I have never heard of anyone needing web pages open 24/7 LOL. Thats why there is bookmarks, and such.

I don't think a web browser has ever been tested like that. With 20 tabs open, 24/7 fore weeks to months at a time.
But some users, use things in different ways. And there is nothing wrong with that. Just try to keep in mind that a web browser wasn't made with that kind of usage in mind. (I think of course, I have no proof on how they think it should be used, so I may be wrong)
Have you updated to the latest version of chrome? Updates may help the memory usage and leaks it seems to have after such a very long time running.
My chrome shows 10.0.648.127 beta
Chrome has to be restarted to finish the update, if she never restarts it, it never updates.
I use firefox myself. I have chrome and IE9. I use them all to test my sites in them. But I mainly use firefox.
CleanMem only helps with the working set of a process. Which is the actual memory being used. Commit charge, This is composed of main memory (RAM) and disk (pagefiles). So subtract the working set from it and you get how much is being claimed for the page file. Normally an app shouldn't need the page file unless there isn't enough memory. But in this case you have a page file leak as well.
All web browsers depend on java and flash. make sure you update both. I think java is up to update 24 and flash is 10.2.
Again the browsers have to be closed to get the updates.

Shane