I'm currently on a business trip so I'm pumping and need together my milk back home safely. Thing is, I'm away for four days and my milk usually starts to go funky after three. I'm lucky to have a full-sized fridge with a real freezer in my hotel room so I can easily freeze milk, but I'm worried about getting it home without melting (4.5 hour flight plus all the extra time needed to get to the airport, get home, etc). I have a cooler and I'm planning to put it in my checked bag because the cargo area usually stays pretty cool. But still...

Anyway, should I: a) freeze it all and hope for the best, b) freeze a couple of the oldest bags I'm worried will go bad, and know I might have to sacrifice them as just extra ice packs in the cooler because they'll probably start to melt, or c) something else? Fortunately I have a decent freezer stash so it's not a disaster if I lose the milk, but I'd rather not lose it if I can avoid it.