Too many tabs opened may make Firefox to run slower or it does take time to reload all your tabs at next restart. With BarTab add-on you can only make desired page to load in the background and all other tabs will kept on BarTab.
1.Open Firefox 4.
2.Type about:config and press enter to continue .
3. Type browser.sessionstore.max_concurrent_tabs in Filter .
4. Double click it and enter its value as 0.