Life span of 5U4G tube?

Anyone know the life span of a vintage 5U4G tube from the 40's or 50's?

spareribs10-23-2008 9:17pm

spareribs OP Details Discussions Posts This discussion Message User 5 posts 10-28-2008 at 11:49pm Copy Comment URL Report Comment Edit Delete Wow, thanks. That seems longer than a NOS 6SN7 tube lifespan.