Pressure is the problem. Duration is not so much. I would wear for 2-3 hours back a few years because it was possible then. To high of pressure at any duration could cause blisters, bruising, redness and will prolong the fading cup ring marks. I would suggest that if you want to wear for extend periods, every 30-45 minutes to reduce pressure for 15 or so them increase it back up. High low, high low type of thing. I have tried so many ways but it still boils down to what works for your time table, your schedule. Find what you like or more correctly, find what you enjoy. There is more than one way to do this. The one thing that is the “only way” is, you have to be consistent in your quest to enlarge!! Consistent is key I have found. Figure a schedule and stay with it!! Use generous amount of oil when using your cups. It will facilitate the draw of your skin into the cup better than creams. Oil will last. Creams absorb to quickly. Use the cream lotions afterward. Pump away my friends!!