Is extremely accurate "VTA" adjustment necessary?

In several instances where I have had others around while seeking to set the VTA, there has been total agreement. I do not think it is so totally subjective as TWL suggests. But I totally agree with him that it is a subjective experience, that you say, "Aha, that is it."

Dougdeacon, yes for most arms the VTA has to be a compromise setting. I once had the Wheaton arm which has an easy VTA adjustment with an easy reproducted marked scale. I did mark many albums as to where they should be set. One cannot do this with the Schroeder so I use the best overall setting.

ok, here's what you want with respect to vta. the stylus manufacturer has decided stylus stip shape. maybe spherical, eliptical, micro line,etc. your goal is to have that stylus tip rest in the grove exactly as the manufacutrer intended. thus you will achieve maximum contact of the stylus as was intended. thus you need to have the cartridge aligned perfectly in all planes. Also correct antiskating force is essential.
If vta is off it will cause the tip to tilt forward or backward giving less than optimum contact. Take a good record get the vta right. tonearm parrallel to the record surface while stylus is resting in the grove with correct tracking force and anti skating force. then you need only measure the width of each record and adjust tonearm height for the difference. don't measure the thickness from the lip of the record but from the middle part of the record.

Good, as far as it goes. The challenge is the inconsistency with which records have been mastered over the years. As has been commented on already in this thread (Doug, I think) a standard was not adopted until later on in the LP era and even then not all mastering engineers rigorously followed the standard. So you have cutting angles anywhere from 20 degrees to 23 degrees, and thus variation from some LPs to other LPs even though they are the same thickness.
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Gregadd:

I believe that there is a "play" area as far as VTA goes. VTA to me is then a tone control/balance adjustment.

The interaction between various LP grooves and various styli is far from being of a consistent nature.

I also DO NOT make "minute" adjustments on an LP to LP basis, and instead use the simple rider mat procedure I mention first on in the thread. However, I would enjoy having this capability if it were easy to use.

The adjustable arm I tried years ago may have been an Alphonsen (sp), but I'm not certain. The deck itself was a higher end Rega. I can't image easily adjusting this arm on my suspended deck (it was tricky enough on the fixed deck), nor do I even know if the arm works well on suspended decks.

I set the standard VTA of my arm/cartridge (standard being a mean of the typical/thicker LP stock I play) using two sets of ears. My wife prefers less treble/more bass than myself and I adjusted the VTA with both tastes/preferences in mind.

I installed coaxial drivers in order to make adjustments, other than that of VTA, as my everyday speakers start rolling off @ around 14Khz. Instead of normal placement the two speakers were placed out into the room, approx. 4' apart, in a triangular near field setup.

I used to have these adjustments done @ a local shop that used an "O" scope along with my test LP's, but the shop and my friend who worked there are long gone.

Both setup methods seem to give the same results, though there was a certain peace of mind having it done @ the shop with the test gear. The shop was also much faster (1 hour VS my few weeks of making further minor adjustments when I felt like it).

I find it impossible to set up a cartridge (by ear) in a single attempt as after a short while I loose my ability to hear clearly. Big difference between analyzing sound and listening to/enjoying music.

TWL mentioned an add-on VTA adjustment device for Rega arms (got the impression that it could be used "on the fly") a few years ago, but I have not read/heard anything further about it.

ok then i concede that the cutting angle varies form lp to lp with no real way to tell. so let's suppose using my method you landed at 22 degrees as optimum. that would leave you with a +/-2 degrees window for any given record.
Let us be generous and say by the golden ear method you are using a one minute passage of music to find the vta.
I could be mean, but I will not. Since you don't want to measure, I assume you have a contioulsy variable method of varying tonearm height. That would mean there is infinite number of settings and assuming you did not get lucky, you could be left sampling an infinite number of settings with no way to repeat them or even be sure you were listening to them all with any real consitency. If you remeber the abx comparator box one of the problems was sonic memory. But let's be nice and assume you have an arm which allows you to divide each degree into tenths. Again assuming you did not get lucky and have it "snap into focus" right away you would have to pick one setting and compare it to the 39 others. it would take atleast forty minutes to do that. That also assumes you were satisfied with only one pass, that you had the sonic memory to allow you to make just one pass and remember where the best one was. Since you don't measure, even if you could remeber the one you like ,how could you find it. I could go on, but i think you see why i am skeptical of the golden ear method.