On the GN, at least for boxcars, it was an average of seven years. The GN shopped their
boxcars more frequently to ensure high quality cars for grain and flour loading. I don't know
for sure, but suspect this would roughly hold true for NP, CB&Q, and Soo Line boxcars as
well. Perhaps Mr. Ehnbom will add more to the discussion.

Sincerely,
Robert D. Heninger
Stanley, ND

I don't really have a clue about this. For what it is worth, box cars with early 1950's paint jobs were still in revenue service on the BN in the mid 1970's.

Staffan Ehnbom