This is one Techsupport question. You could contact them for the detail. However, this is not difficult to achieved, so I think you could try my idea following.
This function could be in exception and compression. Though they are not same way for data compressing, you will get the same result just in this case. There are setting of Min and Max for both this 2 method. You could set 1 hour for Max. This means if there is not value change for one hour, PI server will write the current value into achieve. And this could achieve your goal that not to store all unchanged values during 1 hour.