Potentially a B777-300 could be 5hr 39mins away from the EDTO alternate.
Area of operation is determined by 240 minutes at two engine cruise speed...
240 mins at 490 kits = 1960 nautical miles
1960 nm at ETP1D speed (Single engine depressurised @ FL140 = 5hrs 39 mins
Ummm really? (straight from an Ops manual)
"ETOPS is the acronym created by ICAO to describe the operation of
twin-engine turbine aircraft over a route that contains a point further than
60 minutes flying time from an Adequate Aerodrome, at the approved
single engine inoperative cruise speed (under still air ISA conditions).
ETOPS includes operations over remote land areas and water."
So yes you can exceed the time, but most likely due to the wind component. I'm not sure how you can define the area of operation (I'm assuming you mean the ETOPs segment) as being based on the normal 2 engine cruise speed, unless of course this is a local Oz variation.