Rtic thermos thing good for storing breast milk?

Im not due until December but we do live a good 7 hour drive from family (although I do NOT plan on traveling that far with a newborn so soon) I was wondering if anyone's tried a thermos to store breastmilk for those long drives? Will it go bad? I didn't breastfeed my first due to some issues so I'm at a loss! Or what do y'all do for long drives with breastfed babies???