Dynaco Pas 4 Pre-amp tube questions

I am looking for any current or former Dynaco Pas 4 pre amp owners who can help me with a couple of questions. I would like to replace the 6922s in the line stage. I was thinking about going with Sovtek or Electro Harmonix. I have seen these tubes on sale and they usually say "preamp quality", what does that mean? If I play my stereo an average of 7 hours a week, how long would an average 6922 tube last? Also, I will not be using the phono stage on this pre-amp, can I take out those tubes without doing any harm to the operation of the unit? Thanks! Vlad
Can anybody offer any advice for me on this?

Preamp quality means low noise and hopefully low microphonics. I use Telefunkens in my Pas4. I would not remove the tubes from the phono stage, as they balance the load of the power supply.