We have 4 EVS machines in our facility. The operators like them, maintenance doesn't. The PM's aren't that bad it just that maintenance doesn't like doing them. On a few of the earlier machines we have if the operators are not careful they can get molten solder down onto the control board and into other parts of the machine where solder doesn't belong. That's the main reason why the maint folks hate the PM's on these.
They do save us money and recover a fair amount of solder that would otherwise be headed to a metals recycler. Our wave solder pot analysis results come back consistently looking good.
I don't know of any other solutions besides the ones mentioned. DG