I can't say I'm never upgrading anything more, but I've reached a point where spending more money on upgrades is not really going to improve my listening experience. Most people including your friends and family will never care if you spend their inheritance on a really expensive system because you want to sit there and replay the plucks of a string instrument to impress them with the realism of your system. They will not care, most people will not care about slight differences in your system or music. I'd almost say nobody cares, but nobody in my orbit cares about my system or would even want to sit and listen. It's about me, and I sure will not have my life enriched in any way because of some slight difference in sound and we sure don't sit around talking about the spend. Most people on the planet want to enjoy the music as background and do not want to sit and hear you ramble on about swapping tubes, amplifier architecture, etc. Once you realize nobody cares about what you bought, you'll be in a better place. Once you get past the obsession of buying things, you'll feel better. A huge expensive system may be amazing, but it will add nothing to your life, maybe the opposite.
How good is good enough?
Most of us here cannot afford six figure prices for each component (assuming that will bring the best sound.) So how far do we want to go to improve our systems? There are always bigger fish. When does it stop? It stops when we say it stops, when our gear brings us satisfaction. To constantly strive for better sound is an endless quest, not necessarily based on the quality of our set but on our personality.