Wonder if it's been shown:

If a person cycles at a moderate pace for a mid-distance which was initially more of a physical challenge but no longer is due to daily practice, if that translates for the body, as burning less calories?

Would the body become more efficient in burning calories when it "plateaus" at a certain workout level, if the body is not pushed abit more to be challenged?

I'm cycling 42-45 kms. daily for the past few weeks. Only on weekends, I might do a ride that is longer.

No, I do not want to spend more time cycling more each day. Life is not all cycling.