Every couple of days I have been doing Wim Hof breath-holding. I hyperventilate a bit by breathing quick and deep 30 times, then I hold my breath until I feel a strong urge to breathe. It's usually about 2 to 2.5 minutes. I'm not interested in really pushing it, and I am not doing the cold immersion. I just figure it's good to ask a bit of your body in different ways from time to time. A doc named Joon Yun convinced me it was likely worth doing.
Definitely a good idea to push your limits. Use it or lose it is what Dad lived by. I try to as well.