Okay maybe after a while time for change or at least devs could experiment with another world where in study table players could study same items.
As like fill it up with cone cows as it would take 1 mental weight, so fill it up. Also maybe also being able to study stacked curios and they are being studied stacked too, so if 1 curio byitself cost 1 mental weight and it can be stacked to 3, then it should be in total 3 mental weight. Since at some point we will reach huge stats for inteligence, so instead of waisting it, let us max it out with same curios and stacked curios.
As for study desk, let as sort what will be studied next, either by mental weight lowest to highest or highest to lowest or total lp lowest to highest or highest to lowest or lp per hour, you get the idea as right now I have no idea how it picks what will be replaced (which is on devs side need to be explained better).
Not saying make it default if devs don't want to, but at least test it for next world like world 16.2.