I guess you're talking about keeping them fresh until you start juice fasting? Because once you do start juice fasting you'll go through 25 pounds of carrots pretty darn fast lol!
I don't know if you've seen this post that Uny made telling about how much various fruits and veggies yield when juiced. It will really come in handy when you start buying all your produce. This is the first guideline I've ever seen and of course it won't be exact but it's closer than anything we've had before.
I've stored carrots in the humidity controlled compartments in the fridge for a little over 2 weeks with absolutely no problems whatsoever but I've never stored them outside the fridge, sorry can't help you with that. I think NaturalRN's idea of the cooler is fantastic but like she said be careful not to freeze them lol. You could always put ice in the cooler and let the cooler get good and cold then you could stick your carrots in one of those huge insulated mugs, you know those big tall ones, that way they wouldn't freeze.