Delayed recovery and loss of muscle mass don't seem to be associated with cardio, even regular cardio, unless the session becomes too long. 30 minutes seems to be the upper limit my body will tolerate without undue stress, but 15 minutes will leave me feeling fresher than when I stepped on the track.
With all the health benefits and stress relief I get from a bit of running, its really a no-brainer. For us old timers, a few extra minutes on the run might mean a 1/2 inch lost on the quads, but a few extra years on this earth!