The Paviours balance/efficiency doesn't seem quite right at the moment. I'm not sure exactly if it's that the paved roads fall apart too quickly, or the paviours are just too slow, or both.
I've tested out a walled city center, I think about ~100-120m diameter, with 10 paviour buildings, fully staffed with commoners, all with access to stone resources, and they are incapable of keeping the whole area paved. They manage to keep some areas paved, and luckily my citizen's houses haven't downgraded since I increased to 10 paviour buildings.
Proposed solutions: If you're happy with the balance/speed of the paviour's, please increase the amount of workers per building significantly. It doesn't seem right that one town area should need close to a quarter of the space devoted to paviour's buildings should I want to keep it in cobblestone.
Or, increase the efficiency of paviour significantly. Or, increase the duration of paved roads significantly.
I personally don't mind paved roads being a resource sink for stone, I just don't want to spam 20+ road upkeep buildings to make a single walled area look like a proper cobblestone road medieval town.