When I was first prescribed oxygen, I had no idea about the regulations regarding oxygen therapy and Medicare or the insurance industry in general.  I did not know that if I accepted tanks to address the issue of mobility that I could not get a Portable Oxygen Device paid for as well.  I remember telling the technician who delivered the concentrator that I wanted to go to the State Fair of West Virginia in a few days.  He said that I would need about six tanks to accommodate a day at the fair.  I gladly accepted the tanks and it was only later that I realized that this was not going to work at all.
I was concerned about the tanks being in the hot car, but then I realized that this was not my biggest problem.  The biggest problem was that I would have to walk at least half a mile to get the next tank out of the car.  It would be swelteringly hot and it would not take much walking to exhaust a person who did not need to be on oxygen.  I contacted my doctor and it was then that I found out that I was stuck with the tanks and a contract with the oxygen company.  I purchased a Phillips Simply Go because it would produce a 2-liter flow of oxygen.  I calculated how many batteries that I would need and purchased extra double batteries out of my own pocket.  Truthfully on my credit card and paid it off over the next few months.
I was able to attend the fair and haul the Portable Oxygen Concentrator (POC) on the little cart that came with it.  I exercised and built up my strength so that I was able to manage the POC in a backpack to do the weeding in my flower beds and other things that required both hands-free.  Then came the second pneumothorax and a lengthy stay in ICU where I was not allowed out of the bed because of the suction on the chest tube.  I lost all of that lovely strength that I had built up and I was not able to stand from a sitting position without help or holding onto something to help pull or push me up.
I once again built up my strength and was able to get off the oxygen.  Getting off oxygen was a very pressing issue for me.  That goal kept me exercising and living a very healthy lifestyle.  Then came the third pneumothorax and a lengthy stay in ICU.  When I got home this time I was not as weak as I had been the time before, but I was not strong enough to manage the 10 lb POC in a backpack.  I then graduated to the Inogen G4 as I had learned that I could keep my saturation up with a pulse dose.
I purchased the hip bag for the Inogen.  The fanny pack as I call it was a tremendous improvement over the backpack for me.  The Inogen is slim enough that I do not have the issues of knocking things over and not being able to get into some close quarters as I did with the backpack.  I also do not have the issues of my back hurting that I did with the backpack.
I have continued to exercise and have built my strength back to where it was prior to the last lung collapse.  I have not gotten off oxygen and that is no longer a major goal.  One reason is that there is a slight chance that being on oxygen may help prevent another pneumothorax.  It might be working because it was 3 years in March since I had a lung collapse.  Prior to this, I had a pneumothorax every 2 years.