I unplugged it last night and let it sit in my living room for the past 24 hours. Some residual heat blows on/past it from the propane monitor heater only a few feet away. This morning it read 41 degrees. Checked it again a few minutes ago and it now reads 51. So less than 1 degree per hour with heat blowing on/past it. Jill sampled a glass of apple juice from the cooler and said the temp of it was just fine.
YMMV due to ambient temps, items inside holding the cold, direct/indirect sunlight, etc. but so far I'm happy with the ginormous cooler.
When you load up your cooler for your adventure, I'd recommend putting a gallon or 2L bottle of frozen water. This will help sustain the colder temps during non-powered times. Plus you'll have ice cold water when it finally melts.
Keep an eye out on www.openboxdirect.com for wicked good deals. Search under their scratch and dent appliances.
Or look through www.compactappliance.com for "new" items.