I sometimes declare myself the winner before hitting 60% If I've broken the back of my only major opponent.

In my Scotland campaign, I had the largest army, navy and income, but the Crusader States had a huge standing army 19,000 strong concentrated in one province, the heart of their power. I mustered about 9000 defenders in the territory net door to bait them into the attack.

Attack they did. 19000 worth of knights, halbardeirs, crossbows/arbalesters, men at arms, foot knights and Order Footsoldiers. the battle was a bloodbath, and by the end of it, almost 12,000 crusader were killed or captured, and 3000 odd Scots. In one major battle I had crushed the vast majority of their forces, while my resources were still undepleted.

From that point on the outcome was inevitable, as i out earned and vastly outnumbered them, plus had control of the water so declared byself winner rather than slowly grind them down.