You don't mention why you were put on oxygen.
I first was put on oxygen for sleep after lung cancer surgery (3-month prescription). Had a second lung surgery and again had 3-month prescription. Then I had radiation and experienced radiation-induced pneumonitis. My pulmonary function tests stayed down, and I was diagnosed with pulmonary fibrosis so now I have a permanent prescription for oxygen for exertion and sleep. I don't need oxygen while sitting.
It depends on the reason you were put on oxygen. In my case, pulmonary fibrosis is a permanent disease.