Tire Pressure Gage

I have a pressure gage on my tire pump but have been wondering about
whether a separate pressure gage might not be helpful. 700C 28 or 32,
presta valve, tires, at ~90 - 100 psi, and I've pumped them up
approximately every one to two weeks mainly based on the "Squeeze
Test".

I've noticed that connecting the tire pump to the tire and pumping
that the air pressure in the pump and hose rise until they overcome
the tire valve and for an instant the approximate tire pressure is
registered and sometimes if I had known the tire pressure I wouldn't
have used the pump. Thus the thought that a gage might be useful.

On the other hand, it does take a finite amount of air to operate the
gage so each time one checks the pressure it reduced the tire pressure
by some figure.

So the question is whether using the gage with 28 - 32mm tires is
going to cause a significant pressure loss over, say 4 or 5 checks and
will it, in fact, result in fewer pump-ups... not that pumping up
tires is really that onerous a task :-)
--
Cheers,

John B.