RE: extension instead of switch?
Maybe I have been lucky, but over more than 25 years of R/C flying I have never had a switch failure.
Maybe it is because I always mount the switch inside the fuselage, using a pushrod to actuate it and using rubber grommets just as I do when mounting servos.
For peace of mind you may consider an electronic switch such as the [link=http://www.rc-electronic.com/html/englisch/unten/zubehoer/diverses/diverses.html]Behotec Power Switch[/link].