Don't wait for the light as the only indicator to change pads! Many a Boxster owner has tied the sensor up and out of the way when they last changed their brakes. They do this because :
1) The sensor costs money to replace and they check their brakes regularly anyhow.
2) They are using brake pads without the drilled area to accept the Porsche brake sensor.
If you think your due, have the pads thickness measured and make a decision this way. Waiting for the light to come on can get very expensive!
