I've been playing OVC for years and see that each cycle is ending faster and faster...
I would like to make some suggestions:
1) Get grad C for free and buy grad B for 1 week;
2) 2 weeks, release Grad A;
3) 3 weeks, release Grad S;
I don't know if it will work, but I think it will last longer. As it is, on day 2 there are players with S items, and everyone ends up leaving.