Hmm, I don't know if there is an option for that. Top Sites is meant to be updated from your history as you browse. I think your best defense is to pin more sites so there are fewer slots for Firefox to fill from history?

Well technically the best solution for me would be using bookmarks over top sites but I prefer the gui of top sites and its easier to navigate than bookmarks. I simply would like to find a way to turn off automatic updates to top sites like in opera or chrome. It's just annoying to delete the sites I visited once

You can set the number of rows that Firefox displays on the Firefox Home page. Best would be to switch to Full Screen mode and then pin websites to all visible tiles. I think that should work and prevent adding extra tiles.

You can paste or type 'newtab*rows' in the search bar on the on the about:config page (too bad that the new html about:config page isn't supporting wildcard and RegExp filters).

• browser.newtabpage.activity-stream.topSitesRows

You can open the about:config page via the location/address bar. You can accept the warning and click "I accept the risk!" to continue.

• http://kb.mozillazine.org/about:config

Well I tested that and ff still saves them even if it can't place them on top sites if I would raise the row limit all of those sites would be shown. It's simply delaying the problem not solving it :/

If you raise the row limit then you enable more tiles and obviously Firefox will fill the tiles with items from the history based on frecency bonus points. That is expected behavior and all other 'recent' type query lists behave the same way. As long as there is history or bookmarks left then you will see these appear. Don't use the Firefox Home page if are aren't satisfied with this behavior.