How far apart do you position your speakers ?

Here's my formula, try it if you get curious or bored:

Speakers 1/3 into the room
Chair against the back wall (make sure the wall behind you is not hard/bare)
Speakers spread 83% of the distance from your ear to the plane of the speakers directly in front of you
Toe in to taste, I suppose this will have a lot to do with speaker design

My room is 13' front to back, 12' side to side.
My speakers are a little over 4' into the room and are about 68" apart center of driver to center of driver.

I went to a shop in another city a while ago and the owner suggested the 1/3 into the room and chair against the back wall. It went against what I believed, but I got curious and bored at the same time so I tried it.
I got the 83% thing from this thread and it actually worked pretty darn well.
It may be that my room is small, a cube, or whatever but this is where I have my speakers.

Is it that the distance between the speakers is 83% of the distance from the speaker to ear or plane of the speakers in front of you to ear? There is a difference.

I did the plane of the speaker to the ear, but I believe the 83% mentioned in this thread was from ear to speaker.
The way I did it worked well for me. I have my rack on the side wall, so moving speakers farther apart would have meant closer to the gear.

I find that a listening distance of 1.5 times the spacing between speakers works best.

If you listen at 6 feet then speakers spaced 4 feet, at 9 feet spaced 6 feet apart, and at 12 feet spaced 8 feet.

I find the often recommended equilateral triangle with toe in does not sound as realistic.

I prefer speakers facing forwards and square to the room - no toe in or toe out.

I do not respect speakers that change their sound character with angle.

I will only use speakers with even dispersion across the main frequency range.

As far as they need to be.