well when they did it to hear where I was, I didn't mind it so much, but now they have been so spoiled, and keep it going even after I answer them, it bugs me, I have to ignore them to make them stop, as long as I know they don't need food or water, and nothing is wrong... sometimes Charlie or Louise will do the crying thing around 4 or 5 AM til I want to yell, then I see they are out of food, and then I feel bad... not often but sometimes the dish runs empty in the middle of the night!
lately some of them do it because they are bored and want to play. Charlie and Cassie especially lately seem to be needing more attention...