Couple things about this, plenty of errors/warnings scrolling by are no big deal, Mint is dealing with them and nothing to loose sleep over. Some are not and the hint as to what's going on could help you figure it out sooner. Such a scenario, say you install another version of Mint, xfce or cinnamon or whichever alongside one you've already got and you allow it to format the swap partition. No biggie right ? Wrong doing so will change the UUID of the affected partition, thus the one you've got in your formerly working Mint OS's /etc/fstab file will be wrong and systemd will run a seriously annoying 1 1/2 min startjob, while it complains about this.OT: ( yep off-topic) but another tip, cause Colorado seems like the kind of person up to the gnu/Nix challenge, not afraid to get in there and dig around kinda guy and could benefit others as well. As with cli package management, during the boot process you can get to see some interesting information scroll across the screen that you won't if you leave the pretty splash-screen in place. It's a matter of editing one file. ie: "gksudo your-text-editor /etc/default/grub" no quotes in the commands used and your-text-editor is whatever text editor you want to use ie: gedit, leafpad, nano etc etc.
Opens with sudo priv's ... you'll find this line GRUB_CMDLINE_LINUX_DEFAULT="quiet splash" . Change it to be this GRUB_CMDLINE_LINUX_DEFAULT="" In other words just remove the quiet splash part. After you edit this file you have to run the following command in terminal for the edits to take effect, "sudo update-grub", once it's done, reboot and instead of the pretty splash screen you get to see all kinds of mystical looking text scroll by as the Mint operating system goes through booting up.
Sometimes these will show you important errors too and/or give you hints about something that's going on, that you may want to address. If you ever want the splash screen back just reverse the process above, put "quiet splash" back where it was, update grub and whamo !!!
So ends up your boot-up suddenly takes 90secs longer until the UUID in that install's fstab file is corrected. If you have the splash screen up, you don't see systemd throwing a fit and you don't see the error that you can then google to lead you to the simple solution.
Also and as an added bonus, anyone watching (family, friends ... dude sitting at the next table at Mcdonalds) who see all this mysterious stuff rolling across the screen while you're booting up and again much more briefly when the OS is shutting down, will think you are an UBER L33T hacker type person. While you (and I certainly didn't) won't have the slightest clue what any of the lines of text scrolling across the screen means for awhile. Just play it off, they'll still think you're L33T! and actually in taking an interest in this type of junk, you are in fact one step closer to being a true geek or junior neckbeard !
You'd definitely catch any such startjob running errors though. So it's a win/win kinda thing.