The Windows Backup does do incremental backup, so in future it will only save any changes that have been made since the last one, and won't take anywhere near as long.

You may, at some time in the future, want to go through the settings of what exactly gets backed up, because I have found that the default settings back up a lot of stuff that I suspect many folks aren't bothered about. Stuff like your music collection - I already have mine backed up in two different places, I really don't need yet another backup.