I'm personally unsure why skilling up isn't a bigger concern for everyone... With the minimal to nonexistant stat boosts we get from 75-80, I'd say the bulk of our power increase comes from the higher skill levels. Magic is easy enough in besieged, but for weapons you simply need more time... I personally have no idea how to efficiently go about this, but I'd really like to find a surefire way because keeping my weapons capped is almost as important to me as the leveling itself. In an hour in Abyssea I managed to get 1.5 GAxe skill (although the entire hour was not devoted to skilling). This isn't a realistic way of skilling up however because of the always-in-effect time limit...
