Your description of gradually fading brakes over time is consistent with need for a brake adjustment. When bleeding the brakes, did you bleed the hydrovac? Supposed to bleed that first and it usually takes a pressure bleeder or a lot of patience on the part of the wife/helper. Air in the Vac probably wouldn't cause the hard pedal symptom you describe but when the dust settles on that problem, if you have mushy pedal, bleed the hydrovac, then do the wheels from farthest to nearest the hydrovac in that order.
