NOS power tubes are very expensive, so those are not an option for most people. You would always want to use the same brand of power tubes in all positions, but, depending on brand of gear, you sometimes can substitute a tube or two of another brand in an emergency.
Small signal or preamp tubes can have different functions and different amounts of effect on the sound in different positions in preamps and amps. So you may be wasting the sound of your favorite brand of NOS tube in certain positions in your gear. Less expensive and more readily available tubes may work just as well in those positions.
If you use new production tubes they are generally cheap enough that you can use your favorite in all positions or buy different brands to experiment with without spending too much money.
If you go the NOS route, you will still want to experiment, but you’ll want advice from someone familiar with your specific preamp or amp, as experimenting with NOS tubes can get expensive fast.
Small signal or preamp tubes can have different functions and different amounts of effect on the sound in different positions in preamps and amps. So you may be wasting the sound of your favorite brand of NOS tube in certain positions in your gear. Less expensive and more readily available tubes may work just as well in those positions.
If you use new production tubes they are generally cheap enough that you can use your favorite in all positions or buy different brands to experiment with without spending too much money.
If you go the NOS route, you will still want to experiment, but you’ll want advice from someone familiar with your specific preamp or amp, as experimenting with NOS tubes can get expensive fast.