I used to strength train for years. I competed in lifting competitions and even had some scholarships for school (that I foolishly did not take). But now that I'm a little older, I can tell how years of heavy training has taken a toll on the body joints and tiny bones. Speaking from experience, you should rotate through heavy and light workouts. When you drop the weight, just add reps. It actually creates a cardio effect as well as neuro-junction building (which is what strength training is). The cardio workouts causes your cells to produce more of the organelle called "mitochondria" which is often referred to as "the power house of the cell". It is what supplies your individual cells with nutrient based substances for its operating processes (basically). When you strength train, you are focusing on building neuro-muscular junctions which are the "activators" of the individual muscle fibers. The more junctions your have, the harder you muscle can contract, essentially. Where most people find the best results is when you can find the happy medium for you own individual body. When you do cardio weight lifting (lighter weight and 15-20 reps per set) your body will be working on both building junctions and increasing mitochondrial production.
My advice to anyone that asks me what to do with their workout is try a certain type of exercise regiment for a couple weeks at least, and do that for a few different types of workouts and then see which one sends your home feeling the best. And that will be the one you need to be doing. And once you stop feeling so good about it when you go home, try to go through the workout rotations again and find the other one you need. happy lifting!