I have become very specific in my rides and basing each one around my heart rate and my cadence, followed by time on bike.

The distance is not as relevant now... my average speed is incidental in my training rides and the only time my speed is of interest is in a race situation.

A HR monitor is helping me be more effective and build my available power/strength on a bike, as well as helping with being in the right minimum zone to ensure every ride also counts towards a little weight loss.

I am finding big improvements in my riding basing my training on my heart rate - as JuJu says, get a HR monitor and go to town!