After more than 15 years of brewing, I can say that I have a few beers that I feel I have come close to "perfecting" ..... in the sense that I have basically established the recipe, the process, the water, etc... and brew each the same way, almost every time now. And, they consistently come out very well in my opinion, and the opinion of others.
Dark Mild
Bo-Pils
American Pale Ale
British Ordinary Bitter.
American Brown Ale
Probably all in the last year or so though..... so it has taken 15+ years to get to that point, and I have brewed and rebrewed each 6-12 times (or more) over the last 2-3 years, with minor tweaks to settle on what I feel is "the finished recipe."
Of course..... I would be surprised if I don't keep tinkering with these "house beers" on and off forever.