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... only my second Premier League match
You'll probably consider leaving earlier once you've been to a lot more turgid games, or games when you're 4 down, etc and know that staying an extra 5 minutes to the end will mean you get home an hour later due to queues/trains/traffic/etc.
(Luckily the only popular games I get to go and see I can walk to, so I get to stay and watch the turgid football right to the final whistle.)
You're right, I guess it's always nice to stick around and see what a good team looks like.