So I decided to try playing endless hard levels on WbTD.
This is what I got:
After the first leak, I realized that without juggling, it is impossible to last forever. So I just sent the next waves one after another, getting as many in as I could.
You can get farther if you get rid of those money towers, most or all of the warp towers, and most of those electric floors except in places that would block the creeps so you can fit more boss towers in. I would upgrade all my towers to the next level instead of uprade 1 to max at a time as well.