You really should wear it every night, for both physiologic reasons, including high blood pressure in the pulmonary arteries, and to ease your breathing. It can make a significant difference in the quality of your sleep and that, in turn, can be a major determinant of how you feel the next day. There are no adverse effects from using it faithfully every night.
Stella:
Yes, I totally agree with above 's answer, as my husband is in the same boat as you, and even if he takes a np, he has to use the bipap. So, I believe it will sith much less work on the lung/heart by using it, versus the opposite.
My parayers are with you and your family, as I do know how difficult this can be for you.