Originally Posted by Tom K.
For a contrary experience, I've only had to add coolant once to a BMW in over 10 years which includes 5 cars with a total of more than 200,000 miles.
I once got a coolant warning after parking my Z4 on an incline, but it was fine on level ground.
what you've said it doesn't confirm that your cars didn't lose coolant. you've only averaged 40k miles per car, so I can see not having to add coolant in those miles. Cars can lose a liter or more before the low coolant warning comes on, so not triggering a low coolant warning doesn't mean it doesn't lose coolant. Sounds like you just don't check it considering when you got a warning you just parked it level so the warning would go away.
my point is that losing coolant isn't the sign of a problem if it doesn't lose too much.