Conrad Johnson PV11 tube noise

After about 2 hours of being on, my preamp will occasionally give a sustained "chirp" or sometimes a longer high pitched ringing sound, pretty basic tube noise. I typically listen at low to moderate levels, and it is therefore often audible during listening. What can I do? CJ says to use the tubes they supply, because it was designed around them, Upscale Audio says that the PV 11 is a pain with regard to retubng, and He wasnt in a hurry to sell me ANYTHING because of this. It simply cant be that this type of noise is just what you have to deal with when you want to use a tubed pre. What do you think I should do?? Has anyone used a PV 11 successfully with NOS or other non-CJ supplied tubes?? Thanks.