What Mac/OS you on? Try an SMC reset and also a NVRAM/PRAM reset. Those fix about 90% of Mac issues. That’s way too long of time for a backup, are you backing up to a HDD or SSD? Solid state waaay faster and more gooder. Also, pending which Mac you’re using, verify your backup disk is plugged into the USB 3.0 port and not a 2.0 port for faster data transfer speeds. If that doesn’t solve it lmk symptoms/Mac model/OS and I’ll try to support/resolve from there. (Avid Mac user and Phone/tablet/Puter Repair tech.) Also some useful apps you can get to help with all that, using http://www.macbb.com you’ll find any and every Mac app/advice you’ll ever need, free. (: