Using a small amount of vacuum I keep my pump on overnight - to add girth. Reduced vacuum keeps the edema (lymphatic fluid) from building up and creating a donut. During the day I use it twice while creating a higher vacuum - to add to my length.
Do neither of the above until you understand your bodies limits. That goes double for wearing the pump overnight.
I use my pump at bed time, for about a 1/2 hour, to get used to my body’s reaction. This avoids the potential of creating edema which needs to be avoided whenever a vacuum pump is used