Speed and driving style: winding roads, rapid acceleration, harsh braking, can all impose undue stresses on the tyre which can reduce the tyre's life (at 120 Km/h a tyre wears out twice as fast as it does at 70Km/h).
Overloading or under-inflating a tyre by 20% reduces its life by around 26%.
Shocks: hitting kerbs, driving fast over potholes, large stones and other obstacles can be the cause of tyre damage that is not always immediately apparent.