Disneyland has followed in Walt Disney World’s footsteps and have put the text “Early or Late Arrivals Cannot Be Accommodated” on their Fastpass tickets. So make sure that you are able to return to the attraction within your one hour window.
My guess is that they are getting ready to start the same Fastpass system that Walt Disney World will unveil soon. You’ll be able to request all of your Fastpasses 30-60 days before you travel to Walt Disney World.
(Thanks Living A Frugal Life for the pic!)