Getting to absolute zero is tough. Nobody's actually been there at absolute 0.00 , with an infinite number of zeros. That last little tiny bit of heat becomes harder and harder to get out. And in paticular , the timescales for getting it out get longer and longer , the smaller and smaller the amount of enery involved. So eventually , it would indeed take the age of the universe to do it. Also you , actually you'd need an apparatus the size of the universe to do it , but that's another story.