A tire pressure monitor system is just that, a means of monitoring your tire pressures, nothing more. Having your tire pressures monitored constantly versus periodic checks is a safety issue. If you want to pay someone to check and adjust your tire pressures when needed, that's up to you, and most tire shops that service trucks will do it for you. On the other hand, many of us do have a compressor on board so we can do it ourselves whenever and wherever it's needed, just as some of us do our own oil changes, etc.
As for your tire inflation pressures, the best way to set them is to know what your four corner weights, or at least axle weights, are with the coach fully loaded with full tanks, etc., for travel. Using those weights and the tire manufacturer's load ratings, you can find the optimum settings for your conditions. Until then go with the settings on the on the wall.