I have them on a 8 foot door. They stretch out to 71 inches with the door closed seem to work just fine. I do have a safety cable passing through the springs.
Came in a timely fashion, despite not being in stock. Put them up myself, saved over 300 bucks. (Installer wanted 400) I didn't like the website trying to make me get winding rods, for extra cost. I already have some.