For a (more) permanent repair, you need to use a solution which is more pliable when it dries. Rear windows don't flex, so the demister repair doesn't need to.
There's a specific epoxy-type compound for this type of repair - try googling "Rubber Keypad Repair Kit" - or the part number "CW2605".
There's a lengthy post here:
[Link: sandman.com] which talks about the issue (relating to electronics with membrane keypads in general).
Last edited by Lorewin on September 17, 2011 08:30.