[david-given]

In Australia, there are lots of dirt tracks, and it's standard to regrade them ever year after the rainy season. (At which point they're pretty much impassable.)

But those are dirt roads, which are not the same thing as a proper, old-fashioned gravel Macadam road. They can be excellent, and are pretty easy to maintain --- if potholes develop, fill them promptly with the right grade of gravel --- but don't do high speed traffic well. (Gravel is flung up by the wheels, which was why they started gluing it down with tar --- hence tarmac, or tarmacadam.)

Can find a good video of a grader in action, so here's a bad one:

https://www.youtube.com/watch?v=bFoN5LD0Q-w

[bkjelden]

In the parts of the US discussed in this thread - there really isn't a rainy season. They get moisture pretty much year round - snow in the winter, rain in the summer.

So more frequent gradings are needed if the traffic is heavy enough.