Here are some observations from having applied various upgrades/updates on stock SP4s as well as desktops on both the fast and slow ring Insider program. For upgrades, be certain you have more than 50% battery or that you are plugged into the charger before beginning. Upgrades and updates tend to download in the background if you haven't modified your update settings but the after install time, (the actual applying of the upgrade), can be fairly battery intensive . Updates and especially upgrades will possibly not even be seen by your Surface if you are in battery saver mode. YMMV Having a microSD card inserted may prevent upgrades from being seen and if seen, you run a risk of the upgrade process stalling at around 40% with the card installed. My personal suggestion would be to save yourself the trouble up front and remove the SD card before an upgrade. (all you really need to do is disengage it which takes about 1 second) I use a disk activity light on my Surface Tablets but the same thing applies to a desktop the difference being that it would be easier to see on a desktop as they usually come with disk activity lights. To be as safe as possible when getting any updates, but especially a full upgrade like Th2, when the system offers to schedule a restart or "restart now" wait about 5-10 seconds if you plan to hit the restart now. If you delay more than a minute or 2 there is some serious update activity that will begin in the background that is what you normally would see when you did the restart, where it says updating/upgrading please do not turn your system off. In short, after a 1-2 minute delay the system begins applying the updates. Personally I feel that if you wait more than a few minutes to do the restart you should wait 10-15 minutes. It won't hurt anything. By then most of the background activity will have had a chance to catch up. I don't feel it's a good idea to restart your system in the middle of serious read/write disk operations. There is a slight chance for some file corruption.