I am sorry if you thought i was rude, Shirley, i didn't mean to offend or upset you. You asked for an explanation of why it was considered important to train hens not to sleep in the nestboxes, and I tried to explain about the way the structure of the eggshell can allow bacteria through from dirt on the outside, whether or not they are being incubated or kept for eating. Chris also added the point that ventilation is poor when hens cluster all night in nestboxes and thus they are at greater risk from respiratory diseases and parasites. Between us we just tried to give a fuller explanation of your question than had been spelled out by previous posts. We all have different ways of doing things and I thought you were asking for ideas about how to keep your hens clean and well ventilated at night, and why. As I said, Its entirely up to you how you manage your birds and I think they are very lucky to have found such a caring home.
However, I noticed that you say 'Their nest boxes are cleaned out every morning when I collect their eggs.' So I suppose at least sometimes they lay their warm eggs before you get there, on top of the poo or dirty bedding, before you have a chance to remove it from the nestboxes? Even if the eggs don't visibly appear soiled, they will have been in contact with millions of invisible bacteria. It's just my personal opinion that this can be avoided easily if the hens are taught to perch, and this makes things better both for the keeper and the birds.
However, I noticed that you say 'Their nest boxes are cleaned out every morning when I collect their eggs.' So I suppose at least sometimes they lay their warm eggs before you get there, on top of the poo or dirty bedding, before you have a chance to remove it from the nestboxes? Even if the eggs don't visibly appear soiled, they will have been in contact with millions of invisible bacteria. It's just my personal opinion that this can be avoided easily if the hens are taught to perch, and this makes things better both for the keeper and the birds.