On Sun, 6 Jan 2013 06:37:00 -0800 (PST), Robert Macy
wrote:

how to repaire [and prevent future cracking] WITHOUT adding a big LUMP
to the seam?

The wall run is around 60 feet and 10 feet tall. the junction right in
the middle is wanting to crack. Trying to keep from forming lumps on
the wall, I cut down, used paper tape with a layer of mud under and a
layer on top. [Many may remember the problems I had posted earlier. I
tried to wet the tape first thinking of wall paper and how that
shrinks to fit, but wetting CAUSED the paper to 'slide' as it dried
and thus a crack, so in response I took all that out and did it again
with dry paper tape, which did work better. Only had the tiniest of
hairline crack form all summer long only about four feet of run on the
wall only.]

Well this winter as we isolated that section of the house - meaning
cooler temperatures and probably contracting drywall sheets, the
crack(s) opened up with a vengence! I mean over 3 mil separation!, but
worse the crack is the full floor to ceiling AND even now goes up
along a ceiling section which I never had trouble with before. I
suspect in the heat of the summer the crack will close back up, too.

Yes, I know houses change shape with time, but this seems too much to
be caused by 'settling'. My conjecture is is that this is more caused
by 'flexing'. Oh yeah, the seams are ON a stud(s), so there should be
no reason for movement there.

So, my question is
How do you repair/prevent cracking at drywall seams WITHOUT creating a
huge lump on the surface? I already have built up 1/8 inch thick to ++
on these stupid seams.

This indicates that there will likely be a massive Earth Quake in your
area very soon. Once the house is destroyed by the quake, the wall
cracks will not be noticable. Your best bet is to ignore the cracks
while preparing for massive destruction and possibly your death. Now is
the time to buy homeowners insurance, life insurance, and prepare your
Last Will and Testament, and make funeral arrangements.