I understand it, even if you have to drop essences to be able to exchange them thanks to the trade system... so the reward system becomes random.
In my case, I have dropped 3 essences (in total) last week, which means 8 sessions with the maintenance. Since I had already exchanged a lot before, I didnt have enough parchments to keep exchanging.
Result : Almost 10 days to have a single weapon, playing everyday... that was not as complicated in HoO.