We don't use a time limit for max Cont Fuel. Each fleet has a minimum number (in KG's) or % of route fuel, whichever is greater. If weight becomes an issue, it can be reduced based on available en-route Airports... that's the simplistic answer anyway.
As for EDTO/ETOPS. Above 180 min wind is factored so the range circles aren't a static distance. Cargo fire suppression is also factored, 2 engines at Altitude, so you end up with 2 range circles.