I am posting this primarily as information for Garmin as well as other users with my configuration; just in case you notice issues updating to the latest maps. Hopefully, it will work better for you than my experience.
In the past I've used Garmin Express to update my 3597 on a Windows 7 Pro PC and never had an issue until I tried updating to CN NA 2016.20 (Lower 49 States). Since my last map update I’ve upgraded my PC to Windows 10 Pro, current with all updates, and Garmin Express 4.1.8 is installed. I use Basecamp, so I install maps to both the 3597 (with 5.10 Software) and to my PC. Last Thursday I decided to update to the new map ahead of a trip we planned to take over the weekend. The download seemed slower than usual, but it appeared to finish downloading and displayed "Activating". However, it stayed on "Activating" for about an hour with no change in status and no activity. At that point I decided something had gone wrong, so I clicked to close Garmin Express, which gave me the warning that taking this action could corrupt the GPS, but I didn't care at that point, so I closed GE anyway. Thankfully my 3597 still seemed to work, in "Settings" it showed the old map still in use, and the 3597 seemed to function normally during our trip.
Yesterday, after returning from our trip, I tried again and GE seemed to pick up where it left off and after a short period of displaying “Downloading” it started displaying "Copying". The progress bar and time left kept resetting and bouncing all over the place showing 43 minutes remaining then several days and started counting down again; this erratic behavior seemed to go on for about 30 minutes and never showed more than 51 percent complete. I almost canceled it again, but decided to let it run. Then, all of a sudden, without the progress bar progressing to the end and time remaining counting down to zero; it displayed "Complete". I figured my 3597 was probably bricked, but it still appeared to work and in settings showed it was using the new map and Basecamp also shows the new map was installed on my PC and was being used.
Very strange behavior, but as far as I can tell, everything works. Once I use it to navigate around town I’ll post regarding its performance and whether I experience any problems.