Photoshop - The Ultimate UnDo Key

Command or Control Z can always undo something that you didn't like and take you back in time. However, hit CMD/Cntrl Z again and you get a redo.

In the past when I wanted to go back with more undos, I would use the History palette, By default, the History palette will let you step backward 50 times.
Ever wish you could just do this with CMD/Cntrl Z? Well you can and you don't even need to have your History palette open.
The next time you want to keep stepping backwards in Photoshop try this. Use the Alt/Opt + CMD/Cntrl and Z.  This combination of strokes will keep stepping you backwards until you get where you wanted to be.
Want to make the CMD/Cntrl Z do this for you? You can change the CMD/Cntrl Z to function this way all the time.
Go to Edit > Keyboard shortcuts. Find the step backward command under Edit. Select the shortcut key to be CMD/Cntrl Z to replace the standard undo/redo key.
Now when you want to go back multiple steps quickly just keep using the CMD/Cntrl Z. You can always go forward again using Edit Step Forward or CMD/Cntrl Shift Z.