I'm not a frequent flyer so I arrive as early as I can; if you have the time, arrive early you never know if they cancel your flight and need a re-route or there are a gazillion other passangers stranded due to something that may do check-in slow etc... Worst case scenario, you may ask politely to the agents for a better seat or whatever...
As the other says, it depends on a lot of factors which may make your comfortable 1 hour into a fearful one...