Originally Posted by chasm54

If you could incorporate a few hills into your lap, and attack them reasonably hard, that would introduce some intensity into that ride and you'd soon see the difference. Alternatively, just put some intervals into your middle lap - say 6x60seconds sprinting as hard as you can, with 2 minutes recovery between each.

Yes there is a point of diminishing returns. Lots of miles is good, but simply churning out distance at low intensity will take you only so far. Having said that, keep the intensity reasonably brief. The coaches say that the most common mistake is to make the hard rides too easy, and the easy rides too hard. You need variety, to be riding within yourself for the bulk of the time, but absolutely going for it for short periods.