Vacuum gauge?

When I was first starting out as a mechanic I used to use a vacuum gauge
to set idle mixture.  Just maximize the vacuum.  Anyone else done this?
Any mechanics out there know why this is or isn't a good procedure?  I
don't know how it would work with twin SUs.  I haven't used a vacuum
gauge since I developed a "feel" for carb adjustments.  But, it may be a
useful trick for newbies and others who have trouble with carbs.  The
more I tinker with SUs, the more I like them.  They're great carbs.