Critical focus also shouldn't be done from the seated position. It should be done by getting up out of your chair and walking right up to the screen looking at it from a distance of just a foot or so, so you can make out the individual pixels, even though "smooth screen" does an excellent job of making their transitional boundaries smoothly blend into one another, yet not make the overall image blurry.
The 30 minutes of warm up is important, yes, also be advised that perfect focus for the center is not necessarily perfect focus for the corners, depending on your throw (zoom setting). I try to get a good balance between the two, heavily biased towards making the center as good as possible.
Quick, short taps on the remote buttons, rather than holding them down, does a great job of making fine, tiny steps of critical focus easy to accomplish.
In A/V reproduction accuracy, there IS no concept of "accounting for personal taste/preference". As art consumers we don't "pick" the level of bass, nor the tint/brightness of a scene's sky, any more than we pick the ending of a novel or Mona Lisa's type of smile. "High fidelity" means "high truthfulness", faithful to the original artist's intent: an unmodified, neutral, accurate copy of the original master, ideally being exact and with no discernable alterations, aka "transparency".