Where does everyone have to be off to so fast? I go to places like Oulton Park for the Touring Cars and as soon as the last race is over it's a mad rush to sit in a traffic jam. Why? I get out a footy and have a kick about, have a spot of tea, wander about, then at about 7pm (2 hrs after the last race) I set off home with zero conjestion having had 2 hrs of fun instead of 2 hrs sat in a traffic jam.
At the match why not bring a book, go for a shop at ASDA, visit the City Shop, walk along the canal? Then leave in peace and quiet with no queues. I swear you'll only get home half an hour or so later than you would if you'd left at the end and sat in a traffic jam.
Or come on the train and get the bus to and from the ground, probably cheaper and quicker. I park in Heaton Chapel on a match day and get the train in (about a couple of quid). In Manchester within 10 mins, short bus trip to the stadium. No hassle, cheap and quick.
Of course you have a choice and it's completely up to you what you do. I just don't get why you'd want to leave early.