"Serious" seems to equate for some with how often you change gear. I've been doing this for the last 40 years and once you reach a certain point and your main system is making you happy, you seldom want to continue the obsessive upgrade thing. That doesn't mean that I don't listen critically - I do, and other hobbyists sometimes bring gear to my place and vice versa so we can compare. Only occasionally will this reveal a significant change that warrants a revision of a system.
We recently did such a comparison (on my main system) of two excellent phono preamps, a Vendetta 2 SCP-2D and the last iteration of the Herron phono stage. No upgrades resulted!