I cant say for sure how likely that switch is to give out, but I have a CLE that has definitely seen a TON of use before I bought it. The metal plating is worn through in multiple places and the plastic body is showing through, and the switch in question still works totally fine. But, I also don't think leaving it on would be an issue, the meter is only active when your finger makes contact with the shutter button so I assume there wouldn't be a draw on the battery simply by leaving the switch to ON.