According to Official Guinness Records,
The longest flight simulation session is 9 days and 20 minutes, achieved by Aerobility (UK), at Blackbushe Airport, Hampshire, UK, from 5-14 October 2012. 92 pilots flew a total of 22,600 miles, circumnavigating the globe via known airfields in a PA28 Warrior flight simulator.
For a complete list of 2012 records, please visit 2012 Guinness Records in United Kingdom.