I got a nail in a tyre, the pressure drop required to trigger the warning light was approx 4 psi after about 2 days from when I spotted it.

Also I have noticed that the warning light will activate after 10,000Kms exactly to make the operator check the tyres and reset the TPMS irrespective of pressure loss. I found this out in an earlier version of Vagcom. ie. 'time since last reset mileage - TPMS fault code mileage', somewhere in the ABS section I think.

Macdoc.