You could look at has at least 1 page view on your domain within the last {X} days and give them points.
When trying this, it seems I can't combine a date filter with a filter for the number of views. Not in the lead scoring attribute or in active list filtering. I'm hoping to filter for somthing like "At least 3 sessions (or page views) within the last 30 days". Is there a way to achieve this that I'm missing?