You can never have too much cardio IMO. Obviously let's not take that statement to heart and start giving me hypotheticals of running a marathon a day on piss poor diets. Keeping your goals in mind....ie bulking, bodybuilding, sports, etc....I never turn down cardio when the urge strikes. I've been known to turn my little 10 minute warm up on the treadmill before weight lifting into a 10 mile run just because (in my best Forrest Gump voice): sometimes you just feel like running. I prefer sprint work and fartleks myself, but have at it any way you want. 3 miles a few times a week ain't bad, gear or no gear. Cheers,