Usually 2 hours would be enough with most smart converters, but as mentioned above, the WFCO has been documented time and again on this forum for not going into bulk charging mode. Most times it provides 13.x volts which would indeed take some time to get anywhere near fully charged. The 55amp WFCO will rarely deliver full rated amperage, and if it does so it will taper very quickly leading once again to long charging times. A simple plug in meter for one of your DC power sockets will tell you the phase your WFCO is currently outputting.
For the ideal experience when RVing off the power grid, a combination of solar, inverter generator, and a smart charging converter are all key parts of the plan. Power saving devices are important as well, we replaced all of our incandescent bulbs with LEDs and all of our audio/video equipment are energy smart requiring minimal wattage for their usage. On most days, weather permitting, genny usage for charging batteries is rare, our genny is relegated to powering high current draw items for short durations.