[Leica] M rangefinder focusing techniques

["Mxsmanic" <mxsmanic@hotmail.com>]

I notice that when focusing my M6, I spend about thirty seconds checking and
double-checking to make absolutely sure that the two little images in the
rangefinder are perfectly aligned.  I'm pretty sure that this is overkill, but I
don't know how much accuracy is really necessary.  I'd like to know from those
who have much longer experience with the M body just what sort of technique you
use for focusing so that something is indeed in focus without having to spent
two minutes verifying things.  I presume that there is some point at which
"close enough" is identical to "perfectly lined up," but how do I know reliably
where that is?  Rules of thumb or similar suggestions for speeding up the
process are most welcome.  I've tried checking the DOF indications, but that
takes as long as my attempts to get things perfectly aligned, so that doesn't
seem to work very well.

For example, when focusing at something 200 feet away, I note that the focus
point isn't really at infinity, but in fact is very, very slightly short of
infinity, but I'm never quite sure if I should try to make the adjustment.

It's different from an SLR, in which the image is as sharp as it looks.  In a
rangefinder, the focusing is extraordinarily accurate for shorter focal lengths,
and apparently a large discrepancy in the rangefinder may correspond to a
virtually infinitesimal difference in the actual focus plane of the lens.  Not
knowing how close I _really_ am to acceptable focus gives me enough of a complex
that I miss some shots while I try to see if those two images are _perfectly_
aligned.