I don't understand what you mean, replacing the valves by putting higher quality gauges?
I don't think there is anything wrong with the gauges, so long as they are not over pressurized. I recently sold my MA957 after several years of use, and never had an issue with it. I would buy another in a minute if I needed a CO2 regulator, especially at that price point.
Granted, I was not using the original installed needlevalve as I installed a dual manifold/needlevalve setup so I could use the system on multiple tanks... but even the dual system used the same jbj needlevalves and I never had a problem with them.
Personally, I will still be looking towards a nearly emptyCO2 tank... seems like the most likely cause to me, but maybe I was just really lucky with my setup. Even if there is some left, you would only be out $5 or so in CO2, and considering it ran for a year, it would be worth a try to see if changing the tank fixes your issue. Even if it doesn't, you know you have at least another year's supply of CO2 ready to go.