What is the average "lifetime" of a train boxcar?

Question

I always wondered just how long a train boxcar is used before it is considered "unserviceable."

Answer 1

Railroad rules regulate that each boxcar, or each freight car for that matter, have a service life of no more than 50 years. (Thanks for the  update HOGHEAD. I thought I was forgetting something, I just coudn't figure out what it was)

Answer 2

50 years is the statutory maximum.

Every ten years the car has a major overhaul, called COTS, which stands for Cleaned, Oiled, Tested & Stencilled.  This information is displayed on the side of each freight car.

Answer 3

Longer than the average person.  They are retired/scrapped when it costs more to maintain than to replace or when advances in technologies make them obsolete.  They have a hard life, but they are quite adaptable and usually go through some sort of transformation/rebuids during their lifetime.