These days the construction depreciation is added on by the ATO whether or not it is claimed. I suspect the Accountant doesnt want to do the hard work. Scott (Depreciator), where are you?:p
And of course, if you never sell then that is even more reason to use it.
I don't understand it either. If you are able, you are crazy not to depreciate, and replacement has nothing to do with it. If it breaks down, and your lease allows it, there is no need to replace it if you dont want to.