According to the National Transportation Safety Board (NHSB), there are 24 states, New Hampshire included, and the District of Columbia that have driving record retention period and look back periods of 10 years or longer for driving while intoxicated convictions.

The NH Division of Motor Vehicles did not list the exactly how long a driving DUI or DWI stays on your NH driving history so you will need to contact them to see when, if ever, a DWI conviction comes off of your driver's history.