We have a mechanism that puts the backup into the background when you need the resources on your machine. And in case of an unexpected reboot (which I tested heavily, with a lot of different scenario's) the backup will fail but always succeeded on the next run.
We like to keep notifications low-profile and as less as possible. We only want to show a popup or notification when it is really necessary otherwise people will click it away...
I do understand your concern when installing things or updates, that it is better to postpone the backup for a period of time (maybe after reboot?) so I will take this with me for discussion on next versions