Mike, the manual says that the maximum burn time on "low" burn is 55 hours for a 55 lbs. hopper. Unless there's some fancy algorithm of which I am not aware, that's a pound an hour on the lowest functional burn setting (which the manual says will vary somewhat by installation and pellet quality; the lowest functional feed setting for your stove might be, say, a feed rate of "2" on the dial as opposed to "1".) As Smokey says, assuming a linear relationship, the feed setting of "4" as recommended by the manual for the most efficient burn would burn 4 lbs. an hour- or 10 hours per bag.
We have the corresponding free standing stove, the Napoleon NPS40, and I guess that's about right... to be honest, I've never timed it out. We typically run our stove at feed 4, damper 3, blower 3. We often shut it down during the warmest part of the day to dump ash out of the burn pot, vacuum out the fire box, clean the glass and empty the ash pan. That only takes about 5 minutes to do- but the stove is shut down for a few hours prior to that cleaning. That means that if the weather/winter is relatively mild, the stove is shut down for a few hours pretty much every afternoon. We fill it up before we restart it. I guess we use about a bag a day- about a 40 lbs. bag in a 24 hour period- which is less than 4 lbs. an hour by a straight up calculation, even allowing for up to 4 hours of down time while the stove cools.
During really cold periods we let the stove run for a few days in between cleanings. I'll try to pay attention then to how many bags of pellets we use while running continuously 24/7 on feed setting "4."
BTW, Mike, our son and his wife live in Lynchburg. Our son lived in Madison Heights when he was in grad school. Beautiful historic houses in Madison Heights!