Possible reson for carrying two keys: If your car is cold, start the engine, lock all the doors via door switch, then unlock just drivers door and exit. Lock driver's door with second key and leave the car warming up.
Does require two keys and ive done it once or twice. but i only got one master and one valet with the car, so this requires ALL my keys!
If your worried in any way. Blank key cases are under £10 on ebay, a decent locksmith will cut it for about £10, and the transponders go for £10-30 on ebay, and can be reprogrammed by your car (you must have a master key, method earlier in this thread i think).
Loss off all master keys will set you back around £2000 according to Lexus (new ECU and everything) im sure it's possible for half that, but thats still a massive wedge for a lost key!
yep £2k is what i was meaning- having to replace the all the electronics just to be able to start and enter the car. another example of technology going bakwards and our throw away society- ala concorde.
i dont carry 2 keys thats but have been caught by the ignition barrel fault! wish i did do then! its something i always look for when thinking about buying a car for this very reason- expensive to get replacements!!