[Boatanchors] Question for Eimac 4-65A Tube

[William Morton]

Hello Everyone,

My son and I have a question regarding firing up the filament of a 4-65A tube with no connection to the grid or plate (and no plate cap heat sink, either):  If we light up the filament and leave it glowing for a long time, is there any danger to the tube?  It would be akin to using it as a nightlight (which we are not).  By a 'long time', let's say 5 hours.

Thanks in advance for any comments.

Best Regards,

William, and Son