I'm suppose to be on O2 24/7, but sometimes if I'm doing a short walk to the car or a chore, I don't always wear my O2. I can tell when my O2 levels start to drop I start to get tired or my legs feel weak. I listen to my body and get back to my O2 quickly.
I will agree this site is a wealth of information. It sure helped me when I was first diagnosed. I come back and read articles when I need a boost.
Good luck and I hope you breath easy today.