I know of one brand that says that it can remain unrefrigerated, but I don't trust that. You want to always keep your GH cool, espeically after it is mixed. If you are out all day, you have your food with your, right? And if you have your food, you have a cooler, right? There ya go. Do what every blue collar brother of the iron does and put your GH in your cooler and you are good to go. I preload my pins before I leave the house and take my shots when needed. If you don't pack your food in a cooler, you can still bring your gh in a small pouch with an ice pack. It doesn't have to be perfectly cold all day, but as long as it's cool, you will be fine. 

Another option would be to take all of your GH at once, first thing in the AM. I don't think this is quite as ideal as spreading it out, but if you are taking 5iu or less, this would work out just fine

UC- Next Level Nutrition