Not exactly what you are looking for, but you can build a segment "Visits greater than 30" and apply it to the table/panel with the date range set to 30 days. This will show you those who had 31+ visits which means there was at least one day with 2+ visits.
Aren't you mixing things up? 30 days does not equal 30 visits for most users. If a user accesses twice on the same day, and that is a single occurrence in an entire month, I want that occurrence in my report.