Hi, not, sure. Usually everyone wants it the other way around, like 237,000 results. If this is a large amount of tabs loading at once you may end up freezing or crashing Firefox or your OS with the amount of data requests at at 1 time.

The only way I know is to clear the Cache via "Clear history when Firefox closes" when you close Firefox.

• Options/Preferences -> Privacy & Security
  Firefox will: "Use custom settings for history":
  [X] "Clear history when Firefox closes" -> Settings

There is an on_demand pref to prevent Firefox from restoring pinned tabs automatically.

• browser.sessionstore.restore_pinned_tabs_on_demand

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

I too have this issue and I have submitted a "Feedback report", I have found that the issue, for me on Linux, is that the last Firefox window closed must be the one with pinned tabs, otherwise the Pins are not there on next start up of Firefox.