would agree with hifiman, the 12au7 series of tubes should last a very long time; not like power tubes where you'll get a few years out of them and they need to be replaced.
would also suggest not to rule out the industrial grade tubes such as the 6189, and 5814. The GE triple mica 5814 black plate is a fine sounding tube. Many of these carried the 5 star rating, for broadcast use. similar to RCA's Command line of tubes.
would also suggest not to rule out the industrial grade tubes such as the 6189, and 5814. The GE triple mica 5814 black plate is a fine sounding tube. Many of these carried the 5 star rating, for broadcast use. similar to RCA's Command line of tubes.