I've noticed that mine will go down the more I come on here in one day. If I can hold myself in check to only come on once or twice a day, I stay up at 92. If I come on repeatedly, my score goes down along with it (like it just did since this is my 5th or 6th time checking my page today).
I think it's directly correlated with your visits (your browsing, answering questions, commenting on others' and your own hubs) and your hubpage's activity (comments others make on your hubs, new original hubs made by yourself, etc.). I'm giving it the same philosophy as wine: Let it ferment. xD