What follows is about as exciting as watching paint dry, but people so often ask questions of the, "How long did it take?," and, "What happened during?," sort that I thought I'd share my own, in nauseating detail.
I'm sharing just so others have something to compare against, time wise. I am sure this will vary based upon your actual hardware. I have an HP 15-g035wm laptop with and AMD A8-6410 processor and 8 GB of memory.
I allowed the version update itself to download through Windows Update overnight, so I cannot report on how long that part actually took.
This morning I was presented with the "Ready to update" message that allows one to hit the "Restart Now" button if one so chooses, and I did. In this case I regret doing that only because, from start to finish after that it took just short of 3 hours for the update to complete and for the lock screen to be presented allowing me to log in.
The beginning of the update is glacially slow. It took about an hour and twenty minutes to reach 27% installed, and this is where the first restart occurs.
Once the restart is complete you come back at 30% complete, with the total moving along to 44% in about 10 minutes time. Another 15 minutes goes by to reach 53% and then you linger there for a while. The second restart came at about one hour and 55 minutes and still showing 53% when it occurred.
Once the second restart is complete it takes about 20 minutes to reach 78% and then remained at 78% for about 30 minutes, then made a slow climb to 82%. At this point total time elapsed is 2 hours and 25 minutes.
It crept up to 84% over about 10 minutes and then stayed there.
At this point I had to leave the room, but when I returned a tiny bit over three hours after starting the lock screen was up and ready for me to log in.
Once you log in you go through a sequence that lasts about 15 minutes that's been common on major updates to Windows 10. You get the quick "Hi!," screen immediately followed by the, "We've got some updates for your PC," screen. Then you transition to the "This might take several minutes," screen with the warning not to turn off your PC, which stays through the next several screens. The next screen reads "These updates help protect you in an online world," and the one following that, "We want everything to be ready for you. The final two screens are, "Making sure your apps are good to go," followed very rapidly by "Let's start," followed quickly by your desktop appearing.
So far I haven't encountered any issues with Version 1709.