To add to the other answer, plot demands have taken a large toll on the Enterprise. The ship gets into alot of freaky and dangerous situations, due to its non routine mission. And at as the most advanced ship of the fleet, with the latest and best technology, it's the best equipped for defense and rescue missions. It has a large capacity for transport (transporter and refugee space). It has the fastest warp drive, so can respond sooner.
This said, Geordi says warp hours. This could be a 1:1 comparison of time & distance in warp, Like two random cars with a difference in mileage in the same time period. But this would not make too much sense considering that Warp is non linear in scale and fuel needs. The Enterprise, out of need and capability, likely travels at higher warp speed a higher percentage of the time. Like two similar cars, one pushed harder and longer than the other, will have different stress, fuel consumption, and emissions output.
A Ferrari driven at 60 mph will have a better mpg and a longer oil life, than the same Ferrari driven at 150 mph, even if total distance traveled is the same. In context of the show and Enterprise D service history, this is what Geordi was taking about.