They also have to swap out meters on a regular schedule by law here in NJ. I'm not sure how the gas repair/replacement costs compare to the electric utilities. On the one hand they are a lot less susceptable to damage from storms and the like. On the other hand the repair work would seem to be a lot more involved, ie excavating, pavement, etc compared to areas where electric utilities are run on poles above ground. I would expect that for gas, the overall repair costs are less.
You also have to factor in the cost of the distribution system that is in place. They still have to depreciate it, cover any debt that was taken out to install it, etc.