You can try to profile it, but the actual time is determined by the local hardware after all: Processor speed, number of cores (which affects only some operations), network speed, free memory - there's no way to predict how much of the time will be spend on each task.
But all of the hardware information is available to the OS. They should be able to track generic profiles of different hardware specs and the times it took them to complete, and then they could pick a similar result to your hardware directx config or whatever, and tell you its going to take about that long. Not hard or complicated at all. Hm.
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