If you purchase the 50 hour All Mountain Niseko United Pass, it is activated when you pass through the electronic lift gates. One hour is initially deducted from your pass. You can use any lift for the next 60 minutes. Once the 60 mins has expired, the next time you go through the lift gates another hour will be deducted from your pass. If you are already on the lifts when the first 60mins expires this is O.K. The next hour starts from the next time you go through the gates. Therefore it is possible to get well over 50 hours use from the pass especially if you plan to hike the peak or go through the backcountry gates. The electronic gates display how much time is left on your pass.
An 8 hour pass is valid for 8 hours after you go through the ticket gate on the date of purchase. This is also applies for the Hirafu 5 hour pass as well. They are only valid for the day you activate them even if you don't ski the full 5-8 hours.