The time it takes to process a video depends on a couple of factors, including the length of the footage, the encoding and the filters you put it through.

Here's an example: A 90 minute PAL (25 FPS) video put through the Deinterlacer (48 minutes), Denoiser (2.5 hours) and Deep Restoration (7.5 hours) filters to take it from SD to HD would take a combined total of about 11 hours.
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You can find a detailed list of processing times here.