Almost as soon as you stop using your CPAP, apneas will reoccur. So, whenever you sleep (even an afternoon nap) you should use CPAP. This means eight hours a night, seven days a week.
In the beginning, you may have trouble adjusting to CPAP and will be unable to use it all night. This is normal and shouldn’t discourage you. Stay positive, over time you will increase your amount of time using your CPAP each night. Recent studies show that the more you use your CPAP, the more benefit you experience.
The bottom line is, CPAP doesn’t work if it isn’t used.