you're assuming that google (and panda) are going to stay top forever, which isn't guarenteed. Bing has been making (small) gains for ages. A couple of years from now google's preferred version of the web might be old hat.
I think that its a bit short sighted of google to return the same sites to the top everytime. People dont search for millions of things. They have a few general interests and search for those. the search terms they use are probably quite limited. If the SERPs never change then they will eventually learn which sites are good... and they will have no reason to go through google. they will just go straight to the sites through bookmarks, or whatever.
for example... if i want to learn the birth date of abraham lincoln i can guess right now (without looking) that google will have wikipedia in the top 1 or 2 sites. so why bother searching on google? i already know what the answer is. i may as well just go straight to wikipedia.
its the same with book searches... i may as well just go straight to amazon.
google are turning themselves into the yellow pages, and i cant see that lasting forever.