If you've had this problem since the car was one year old, my suspicion is that you have a leaky injector which is causing the cylinder to load-up when the engine is shut down. This can cause a puff of smoke (even blueish in color; yes, even a rich fuel mixture can have a blueish tint)on cold startups. Also, it may be a little hard to start on a warm engine. I'd suggest that you remove each spark plug and check the condition/color. If one plug is different in color(usually carboned up or darker on the electrode)this could be a clear indication that you have a defective fuel injector. I'm speaking from personal experience. It is highly unlikely (even with your present odometer reading)that your valve seals are bad; unless you've had problems with overheating, which can damage the valve seals.

Bou Bou