Keeping the lore sheets hidden from the players was mostly a failure.
My lore archive had all but 6 pieces of lore in it by the end of the
game, of which very little was originally contributed by me, although
I had most of it personally by the end of the game.
The purpose of keeping the lore hidden from the start is to give the
players something to discover. But, if you do not give the players
incentive to keep the information secret, they won't. In this
instance, the perceived value of lore sheets was so low that people
were willing to give them away. Oleg the Loudmouth's Lore Archive was
actually an experiment to prove this point.