Fun game, but if doing well, seems like the endgame gets too boring to be able to complete a run.
Eventually it becomes impossible to match (a couple of level 6 towers sitting around along with various lower level ones, gold possibly ran out after desperately keeping on hitting remove basic elements if that was chosen), and then it would be pretty much just trying to arrange them as best as possible to see how long it can last.
However there are too many swap, and enemies neither get a lot stronger between waves. Looking at the high scores... Who has the patience to sit around fiddling two items for so long?
If there is a way to discard items / towers, couldn't find it.