Like Marcus, I'm a member of Team Futaba and I've been using the standard Futaba SWH-13 switches exclusively since 1994 without issue. I've never heard of a switch getting more difficult over time like you're saying, so I have no clue as to what may be happening. It also doesn't really make sense to me as to why disconnecting the battery would make a difference.

I mount the switch as you described. I mount them to the servo tray with a piece of music wire running out the side of the fuse.