newcastlecycling

The answer is "it depends".  For me the best miles I did were those done within a structured program from the late great Mick Chapman.

Outside of that environment, if I do 200 km including two races each week I can sort of maintain the form I have.

If I want to improve on that form I need an additional 100 km or for a couple of specific training sessions (track, efforts, sprints) or an extra race.

However, it is different for others. Some do 600km and seem to do better and others can do 100km and clean up in A grade.