When I disassembled my Mountain bike's front hub (Shimano HB-MT400-B) so that I could clean and re-grease the bearings, I found that the cone on one side was developing pits. There are about 4 small spots (not all in the picture) and it did feel slightly rough before I disassembled it. It's a year old and I've put about 1000 miles on it in that time, mostly offroad in dry/dusty conditions. The grease was dirty.
I know the correct answer is to replace the cone/axle ("hub axle unit" per Shimano) but I am unable to find this part. One LBS I talked to said that it appeared Shimano does not sell this part separately. I also couldn't find any hubs of this model that I to swap parts with.
Given that, I am going to be riding this for a while longer, likely until the hub dies and I rebuild/replace the wheel. I would like to prolong its life as much as possible. Is replacing the ball bearings worthwhile? They did not appear to have any damage or marks. Should I increase the overhaul frequency? How much more life can I get from this hub?