My Ford is going on a 2000 mile trip in 3 weeks. It has been experiencing repeated high fuel pressure CEL codes for the last 5000 miles; I've cleared them. What does this situation imply for mechanical reliability or drive-ability issue if I just continue to drive and clear the codes going forward?

Code P0193 = "high fuel pressure, rail A" - 2006 Ford 500, AWD Limited, 3.0L V6, 263,000 miles, nicely maintained / good condition car.

What causes higher than expected fuel pressure in engine?
Why does rail B never get a code? Or is there only one sensor? Could the sensor just be bad?
Really, is there anything wrong driving with marginally 'high fuel pressure'? (Drive and just clear code when it shows up). Or could I just operate on 3/4 of a tank max level?

Thanks, Cecil