I personally still feel squeamish about attaching gauges to the system -- (what if the schreader valve decides to stick open?... or I get a bad connection?) Plus you bleed off a little refrigerant into the manifold lines with each check.
I vote for leaving the system alone until you notice a difference in a/c performance... like you said, when the compressor cuts out from the low pressure signal, or the vent temperatures start getting warmer. This system works best when left alone.
95 E320 Cabriolet, 131K