They could go twice the same distance, the risk would be roughly the same at that point. It's mostly the complexity and changes that make it more risky once the initial trajectory is in place.
You need a lot more impulse and more fuel to go twice as far. Probably more correction burns. A longer final burn before entering the atmosphere. So the risk of loosing the engine is much higher and probably increasing more than linear with burn time/change of impulse.
