Audio Research hybrid preamps need about 3 days to start sounding their best. If you thought your preamp would warm up in 30 minutes because it has a tube you are mistaken. I have known many audiophiles who never knew this, but thought their system was sounding better by the end of the evening.
The tube in these hybrid preamps has a very long life and if you leave your preamp on 24/7 you will only need to replace the tube once per year. This is a small price to pay for the improvement in sound.
If you don't leave it on you will never know what you preamp is capable of.
Do this before changing tubes. You may be satisfied with the sound.
