How close are you to being to your endgame? My system outline and I'm almost there.

I only change things out when they fail in some way.  My last system I purchased in the mid-eighties, I kept with maybe one or two changes since then, until I had a major meltdown, where my amp, preamp, and speakers imploded.  The CD player failed a few months earlier, which I later found was an easy fix(I didn't know back then).  Outside of many MCs and a few interesting MMs,  that was it until, I don't know, maybe seven years ago.   I bought a few recent pieces of gear, but after owning them a bit, I realized I wanted what I wanted.  I purchased all new gear(still have the original purchases), and am very happy with them.  Now in my elder years, I like to tinker with assembling my own cables and just finished making two Ground boxes, aka, sort of Mike Powell(OCD Guy) inspired design in Cigar boxes.  I will let the community know which cigar box sounds the best( kidding, of course?).

I could easily stop now . . . but if I gave in to upgrade-itis, I would change my Rega P6 for a Brinkmann Bardo TT (lower noise floor), my Ortofon 2M w/ shibata stylus cart for a DS Audio optical cart/preamp system, which can also have a shibata stylus (again, for a FAR lower noise floor).

I might also upgrade my Sonus Faber Cremonas to a pair of KEF Blade or Blade 2 - this would take me from a holographic presentation to one just a holographic but with flatter frequency response.

I'm keeping my near-50 year old McIntosh amp & preamp.

I'll be done when I'm dead.  :) 

I have a music and movie system I'm very happy with but as a builder and DIYer being done is like being dead.  Even if it's a project every couple of years the passion to try something else will always be with me. 

Also, even if you aren't a builder, I imagine a system can be like a hair cut, or listening to just 1 artist all the time.  For those of us who have been able to listen and enjoy a variety of systems we may always want to tinker with our setup.  The trick IMHO is not to buy the most expensive, but spread the money around.  Instead of buying THE single most expensive preamp, buy 2 really good one's that sound different enough you want to swap them in.  Same with speakers. 

@erik_squires stated " Instead of buying THE single most expensive preamp, buy 2 really good one's that sound different enough you want to swap them in.  Same with speakers. "

I agree with this sentiment exactly, limiting oneself to One End Sound Only is a form of Monogamy in audio, where one is Wed to one system and don't quite know how to separate due to past convincing of purchases made, conviction made for the value of the choices. A faux fidelity is made to a material item or assembly of material items. Is the same expressed when one has pulled the trigger on resolving a transportation need, 'no' the eye is usually already on the replacement tool after a short period of using the new transport that has been selected. 

Polygamy for the End Sound to be produced, is much much more liberating.

Not wasting time or energies on defending choices made, and wasting valuable time expressing conviction to choices being made or considered.

Being free to be flexible and build on musical encounters and increase experiences of how much enjoyed music can be shaped in different forms by introducing upstream / downstream devices to create other influences, is a stimulation and generates new enthusiasm. 

Polygamy expressed toward the End Sound, what is not to like? It keep ones ear to the ground and keep one on their Toes.

I wonder how many Monogamy towards the End Sound Marriages shown by users of an Audio System, are actually now in the current time a well established Zombie Marriage?? 

I've been lying to myself, this time for over a year. While my purchases/changes have drastically dropped off in recent years, I now somehow seem to be the owner of Audio Note Quest 300B monoblocks. And I'm already in planning stages of bringing it up to silver level via diy upgrades with top of line or near top of line AN parts, this should be fun!