could you tell us what you mean by 'quality of components'
Obviously there are many things that define quality and this may differ from person to person as to what they are looking for (THD+N, TIM, Channel Separation, power, headroom, etc.). I simply included reliability and consistency of response over time as a factor that I regard as one of the important qualities in an audio component. A tube that changes response over a short time of a few hundred hours and ultimately dies shortly after that, is not the kind of quality I would be satisfied with. Others may be happy to put up with these issues and lack of consistency in sound in order to benefit from the fantastic sound of a particular finicky tube. Their definition of high quality differs from mine that's all (weighted to what they perceive as the "best sounding tube")
The list of components that do not audibly drift in a dramatic way with time is far too long for me to mention. Of course, components do age and they do fail but often they last a good many years. A small drift in power supplies as equipment ages is also well known (which is why components are generally designed to operate accurately within a tolerance range).