In regards to fitness I would start thinking of other exercises you can do to mix it up. Doing only one type of excerise can make your body used to it and not get fitter. Also don't forget you do need to do "impact" exercises to keep your bones strong.

So how about adding walking or gym work outs (these are impact exercises) or swimming to use other muscle groups. All will help you fitness and ability to ride longer.

Congrats on the new bike!