From various web sites...

There is no limit on travel times for journeys wholly within, or starting in, County Durham.

This latest news is dated 20th Juily 2009

Local operator Go-North East are allowing concessionary pass holders to travel before the 9:30 start time on payment of a small supplement.

This is 50p for journies within Tyne & Wear and £1 for journies which cross from / to T&W and Durham or Northumberland.

more info and downloadable pdf leaflet at http://www.simplygo.com/ The scheme is experimental until Sept 1st.