In latest versions of deja dup, there is no window created to monitor the progress of an automated backup. This means there's no way to tell how much is left to go, and no way to stop it cleanly if it is taking too long or if one wishes to resume it later.
It should, I think, still be the case that when an automatic backup is started, a window appears which shows the status/progress, offers details, and gives an option to abort or pause the backup process.
ProblemType: Bug
DistroRelease: Ubuntu 17.10
Package: deja-dup 36.3-0ubuntu0.1
ProcVersionSignature: Ubuntu 4.13.0-32.35-generic 4.13.13
Uname: Linux 4.13.0-32-generic x86_64
ApportVersion: 2.20.7-0ubuntu3.7
Architecture: amd64
CurrentDesktop: ubuntu:GNOME
Date: Sat Feb 3 13:53:29 2018
EcryptfsInUse: Yes
InstallationDate: Installed on 2017-11-18 (77 days ago)
InstallationMedia: Ubuntu 17.10 "Artful Aardvark" - Release amd64 (20171018)
SourcePackage: deja-dup
UpgradeStatus: No upgrade log present (probably fresh install)
If you click on the "backup started" notification, you should be able to see the progress.