I have two medium size (20 gal) air compressors and use small amounts of compressed air every day. Useing these valves as mainline cutoffs allows me to simply unplug the compressor/s until the pressure drops down to about 60 PSI then plug it back in for a single run cycle. This way each compressor only runs a few cycles each week.
It's impossible to keep air hose fittings tight enough to prevent extra cycles and these little valves can add years to your compressor life. It also allows you to keep the compressor indoors without scaring the crap out of people with unexpected start ups! Be sure to use two or 3 wraps of teflon tape.