Be VERY careful with that trick...I accidently hit the 'open all' button on a folder with many bookmarks.....locked up the whole computer. I prefer to use tabs and the "Session Manager" extension to keep my favorite tabs available.
   The "recently closed" option under 'history' also allows me to recover tabs accidently closed.

The best advice I know about Firefox is to study carefully all the possibilities in the myriads of extensions.

One of the most amazing extensions is "cache viewer", which will...ummm... show you the contents of your cache and let you do stuff with it.