Taffy. My fan has never come on after the car is switched off but having said that I also switch off at the kill switch when in the garage and leave the bonnet open. As mentioned on many previous posts on here because the engine is totally enclosed with the alloy panel underneath you cant put a packet of pins around the engine bay and no bonnet louvres there is a huge amount of heat build up. Regarding the o rings I don't think it makes a lot of difference if you get 5 years your lucky, I change mine every other oil service so 4 years you do need small hands.....

Em