This is a finance question, not a car question. What I mean is that as long as you have the funds to invest, you can replace anything that wears out on the car. Most cars are junked when the repair value equals or exceeds the value of the vehicle. On a Civic, this is probably going to be 250k-300k for mileage. I sold a '94 Quest at 200k because the a/c repair was equal to the value of the vehicle (about $1,500). Hope this helps.