I spend more than 7 days there, I see a lot of people say they would only want a day there and then back to niseko. Those people baffle me but each to their own. There is more off piste terrain than you can discover in 7 days at rusutsu, those who get bored simply arent finding the goodness in my opinion.
In saying that you probably should just stay at niseko ;-)
Ps a few of the boys on this forum are organising an informal meetup for the first week of feb at rusutsu if you are interested.