Cardiovascular conditioning was not an issue for many years afterward, even with minimal training. 10 years of next to zero aerobic work of any sort eventually caught up with me however, and while high rep squats (20-30 reps) are certainly better than nothing, thinking that they are adequate heart and lung conditioning for anything beyond a very short sprint is foolishness. These days, I make sure to do enough sustained-heavy-breathing-training™ sessions that a flight of stairs, or an occasional long day of yard work or moving doesn't completely wipe me out.
In addition to the pulling harness, kettlebell snatches are an exercise I enjoy and lend themselves to sustained-heavy-breathing-training™ . At least once a week, I do something along the lines of Kenneth Jay's VO2Max protocol (Viking Warrior Conditioning), or longer timed sets. Once in a while, I'll just snatch for 20-30 minutes without setting the bell down.
Today, I did about 23 minutes of continuous kettlebell snatches with the 1.5 pood (24kg). Nothing special - hand switches every 5-10 reps and pretty slow paced (10-15 reps/minute), but I was plenty winded by the end of it.
I find it interesting that people (who spend far more time on keyboards than at the weight room or on the field) get all bent out of shape arguing the merits of "high intensity interval training" over slower paced aerobic work. I think it's commonsense to assume that HIIT and steady state aerobic work will NOT have the same cardiovascular adaptations. In my opinion, any reasonable person would conclude that some of both would be better than rigid adherence to one to the exclusion of all others. The bottom line is that if you are someone who's sedentary/detrained/untrained, then ANY kind of training is going to be better than nothing, and if your VO2Max is poor, ANY kind of exercise that gets you breathing hard is going to improve it... but what the hell do I know? Lyle McDonald is a much smarter man than I, and he has a series of blog posts concerning the interval training vs. steady state training issue. They are certainly worth your time if you want to learn more on the subject. The following is a summary of his series that contains links to more detailed posts: Steady State Versus Intervals - Finally A Conclusion