The higher you climb, the less WS points you'll have to build. Like Nilatai said, at floor 10, you'd need to get 10,880 points, which is like closing darkness 2,176 times. If you manage to get to floor 80, your required amount of WS points goes down to 880. Fortunately, any WS points you build up do not disappear as you climb floors (unless you store your weapon with the NPC). So if you were on floor 10 and you had 250 WS points and you climbed to floor 100, you'd automatically satisfy the requirements for unlocking the weaponskill.
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A good player is one who understands the potential and the limits of his job abilities, and works conscientiously to use those abilities to the maximum benefit of the party dynamic.