I certainly can't be totally satisfied. I have been in the hobby for a little over 5 years and have owned over 40 machines...most of which are good DMD titles. I feel the same way, no matter what I always want another game that I haven't owned or a very nice condition game. I have been burned several times on sales, either paying too much or a bad trade. Overall I like the hobby but constantly wanting to change up my lineup has gotten to be a chore. Buying, selling, and driving to get a game takes up lots of time and energy.
I was up to 12 machines at one time last year, also have another 12 arcades. I feel overwhelmed with fixing or modding a game. I never get to a point where I can just he satisfied with what I have. It seems that my need to sell and buy never stops. I hope to get a steady collection in the near future and stick with it.
I blame all of the great machines out there, if there weren't so many good games then I wouldn't be inclined to switch up the lineup so much. Some of the new games are making people sell off older games and forcing change in the market. One thing is for sure, I can't afford to buy new 8k plus games. If the prices keep going up then I won't be buying new anymore.