I use a Topeak Joe Blow Sport, the yeller one

The gauge works great, the head doesn't leak and when you pull it off, it actually springs out with almost no release.

Anyway, I fill my roadbike with 92 psi and when I release, it's about 91 psi. When you use a pressure gauge other then your pump, it takes pressure out.

I say, press your tires everyday and know what it the soft texture of your rubber and the pressure behind it. You might find it best to squeeze the sidewalls to check it, but just do this constantly to keep a good track what is full and what isn't.

Since I'm running thornproof tubes, my tubes deflate about 0.2 psi a day. I only top off every week or for a good ride. Always deflate some before you inflate.

I also use a portable pump, but I've only needed to change a flat once and it only pumps up to 90 psi or so. So then how far I pump it, it won't hit over 100 psi regardless.