One catch is that it is real-time recording. Unlike ripping a disc which can rip the image at a faster rate, from the DVR, it'll take time, no less than the program length. And it can't be programmed, ie, you can't record a bunch of shows overnight. You need to start fresh with each recording. Depending on the size of the drive hooked to the receiver, that could take roughly forever.
A 2 TB drive, transferring 8 hours a day would take probably no less than 250 days! Goodness help you if you've recorded SD programming!
You have to watch the program and send the video to the DVD recorder (or computer encoder). It is a real time thing.
If you prioritized what you wanted to watch most, you can obviously do it in less time, but it won't be any less than the length of your programming.