I run half marathons in 2hrs, I weigh around 84kg & I do weights as well. Usually for the months of June-July I will cut down on my half marathon training to focus on weights coz I'll be doing field events, specifically the javelin. So for me, I can't mix my 3-hour LSD runs with weights. Does 3-hour runs qualify as cardio ? If anybody here can run for 3 hrs at 7:00-7:30/km pace then do weights, well...       

Of course. But it depends on the individual, what is LSD pace for some might not be so LSD for me. Some ppl might be fit enuff that a 6:00 pace can be their LSD pace. But that is already my half marathon race pace. So for me currently, 7:00-8:00 is my LSD pace, last Saturday I ran 2hrs at 7:24 average, my first long distance for the past 3 months. & U dun really see ppl my size running half marathons.. I'm not saying there aren't, but runners normally weigh less than 70kg... & there are some lighter runners who runs slower than me... Of course going faster is only natural as I progress..