Just spent a few nights at PH Niseko out of season. It's quite cheap when the snow is gone -- I paid something like JPY45,000 a night all-in. You can use it as a base to explore the neighboring countryside but will definitely need a rental car or you'll be stuck at Niseko with not much to do, especially if you are not a golfer. It's also very quiet in the off-season, there was maybe only one other room occupied in the entire hallway my suite was in. The in-room onsen, which is not a feature of all suites (or any regular rooms), was quite nice to have.