browser.sessionstore.restore_on_demand = False
When I tell my browser to run, I want it to load all of my previous tabs, as well as actually load the tabs. When I switch to it, it should be fast, because it as already loaded the content. I don’t want it to flash and load upon my selecting the tab; it should already do that!
There used to be an option in Firefox’s preferences for changing this, but it was removed from the gui. But it’s still there in about:config.