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

audiofeil Details Discussions Posts This discussion Message User 4,011 posts 10-29-2008 at 01:04am Copy Comment URL Report Comment Edit Delete >>You can probably expect a 20 year lifetime from major-brand NOS 5U4Gs.<< Perhaps. Life expectancy depends primarily on the number of thermal cycles (on/off) and hours of use. It could last 5, 10, 20 years or even more.