When were the last 86' high-cube box cars built by Thrall Car and Pullman Standard?

[Andrew Falconer]

When were the last 86' high-cube box cars built by Thrall Car and Pullman- Standard?

From photos on websites like http://www.rr-fallenflags.org/ and http://freight.railfan.ca/ it looks like many of them were built between 1964 and 1972.

Has CSX retired and scrapped most of the 86' high-cube box cars from predecessor railroads of B&O, C&O, L&N, SCL?

How long can CN keep using their fleet of CN, DTI, GTW, ICG fleet of 86' box cars before they all need to be rebuilt or replaced.

Are those CN 86' box cars kept entirely on the CN rail system?

How long will the Union Pacific keep their 86' box cars in service before having new box cars built?

Thank you.