I've had both a starter and a kill switch fall apart this year on my '05 WR. I know the Yamaha UK Enduro team really well and those guys tell me that yes, it's pretty common.
My partner rides a TT250R and the switches on her bike seemed much more robust, so I picked up a used TTR switch on ebay and wired that in using the connectors from the broken switch. That's been fine so far and has a more solid feel. Only minor downside is the "Run" on the TTR = "Kill" on the WR and vice versa.