When is your Hifi good enough?

When it's a quarter to 11:00pm, you're listening, thinking..."just one more" and you know you have to be up at 5:00am.
 If this becomes a regular occurrence, I'd say you're there.
😊

it's never good enough and it's always more than good enough...can always be improved, but as long as that doesn't distract my total enjoyment at what I have, all is well...

"Targets"...??!!!
It's always about the music &, as chayro mentioned, while funds & interest allow.
I suspect we will always be curious... (For some that may also be in a sexual sense...)

Doesn't it depend on what your objective is in having the system?
If it is to have the "best," I think it is an endless pursuit. Like the saying that one can never be too rich, too thin, or too good looking. (I disagree about the 'too thin' one, but you know what I mean).
If the aim of having the system is to listen to music, rather than music being used as a reference to judge system quality, I think you can reach a 'good enough' point that makes sense, whatever your budget. It doesn't mean the quest stops, but the focus changes- more interest in hearing different (and new to you)  music and recordings, rather than using the same set of references, more interest in exploring different pressings and masterings of favored recordings (a factor that makes a significant difference, sometimes more than a gear upgrade) and more focus on non-gear aspects of the system when listening to it. Does that mean that one becomes complacent? I don't think so. I can still hear the shortcomings, the weaknesses, in my system and others, but often, those shortcomings are in the recording itself, and throwing money at gear and tweaking will not do much to change that. It is nice not to be on the merry-go-round, but I also understand the thrill and challenge of the gear pursuit. The problem, in my estimation, is that if the objective is largely if not entirely on the system's performance and possible improvements, that's where you stay focused. I know, from hanging with the  "audiophile" crowd for a long time there is this belief that, if only I get to X place, I can then enjoy it. And that X is never achieved, because it is a moving goalpost- some audiophiles do have the time, energy and resources to constantly tweak, upgrade and reassess-- and are deep into musical enjoyment of their systems. Some of those audiophiles are on this board. And to them, I tip my proverbial hat. Because they can pursue more than one goal at a time. That isn't so easy, is it? 

When it's ten at night, the lights are out,[the little LEDs on the equipment and the tubes on my Mac MC60s are enough]-and I don't have to get up the next day. I don't have an uber expensive system, but it blows me away. Good enough!