Dunno, but maybe I was just plain lucky (or stupid) when I replaced
the kitchen cabinets last fall. I cut off the old valves, cleaned the
pipe and soldered on the new ball valves (two pointing up, one
horizontal), no special technique except to use a "Turbo Torch" fed
from a 20# barbeque tank - I hate the little 14 oz. bottles when doing
serious work.
Gerry :-)}
London, Canada

Was recommended by a plumber to never a put valve in a horizontal orientation
if you can help it. Horizontal orientation allows sediment to settle in the
valve and can result in binding or less-than-full closure. Vertical
orientation always results in sediment falling to the bottom of the vertical
run.

FYI,
--
John English