You can make one (self-contained self-rescuer) that would last all day, but you'd have to carry it behind in a wagon.
I like first class, but I don't like first class people - I prefer the people in coach. I like fine restaurants, but prefer the taste of McDonalds. I like to be perfect, but I don't like perfection - I think it's dangerous. There is nothing after perfection. I know, I am a walking contradiction.