With the cap off, you might give it a tiny shot of WD40 before airing it up. It'll help re-seat the seal. If you've got steel stems, I just saw a gizmo called a SpiraGage that is, essentially, a pressure guage indicator cap that stays on while you're rolling.
I'm probably going to buy one SpiraGage just to see how it holds up off-road with a few scrapes in the brush. If it works out, it's a lazy-mans way to check the pressure without much effort which suits me fine.