Tom_milehigh saidIs this "correct" ?
As to "getting into good habits" -- I think that with a 19 year old metabolism and heart, "good habits" can just as easily mean going to the gym regularly to lift. I would say that was sufficient to satisfy the "good habits" goal.
And while everyone's metabolism slows down, everyone is different. My metabolism slowed down, but that doesn't mean I need to do cardio to keep the fat from accumulating. It went from warp 7 down to warp 2, but it's still faster than the speed of light. What did go is my joints, and I so don't need extra pounding on them doing cardio that I don't need to keep my caloric balance. I'm 48, BTW, and I still don't do cardio. But that doesn't mean I'm going to project that prescription on anyone else.
I also don't think it's a good idea to set up a workout regime based on suppositions about what's going to happen to someone's metabolism 20 years from now, based on statistics about the average male. Average is a mathematical concept. Rarely is any individual "average."