[Sean]

Here is some usefull information about the statistics mod which the Author wrote in a post over at vbulletin.org

The amount of your post count has nothing to do with activity.

Remember that 100% activity means that you've visited and posted 'X' times each day for the past 'Y' weeks. If you've recently missed a post or visit, you cannot achieve 100% activity untill 'Y' weeks after that date. Especially if you've only missed once, it may seem like your activity bar is stuck, but if you keep active it will eventually rise.

You can't spam it up.
The activity bar is updated once per day, at midnight GMT. Your activity for today is shown in your "today" bar. Also note that once your today bar is full, you cannot recieve anymore activity credit for that day. It takes almost 'X' weeks to get to 50%, and you cannot miss a point for 'X' weeks to get to 100%.

This all depends on your settings. As for the longivity, make sure that your member that has 100% longivity doesn't have a join date eairler then yours.