That's a pretty optimistic estimate. I did 100 runs one day and I got not a single rare tower chest, I took 2 day break from farming SBA after that disappointment.
Hunter's Stake and the SB axe took me the longest. About 6-7 months for both of them I believe. Midas curse didnt actually take me that long to get.
Well Midas only took me like 2 or 3 days xD. Also they added Midas to the chest in the Dreadfool's Labyrinth and I believe the drop rate is higher from those but idk.
It's more preferable to farm it from those chests because you will always get something even when you don't get Midas' Curse. How many hours did you farm each day?
I think I did a full day at it. The other days I kinda just meh'd it cuz I didn't know if it was actually a true drop or people were just trolling. And those chests only give you potions but I guess that's good.