Is it ok to leave my dogs in the garage for the night?

We live on an acreage, and have 2 large breed dogs. 1 is a scotch collie, the other a golden retr'vr. They are both 1 yr old. I am home with them all day and take them for at least 3 walks a day, and they are outside all day. We have beds in the garage for them and its finished, and i put a night light on for them too, but I still feel bad sometimes!! Is this mean, or are they ok? I was letting them in the house, but they are filthy! They have black paws and they bring in so much dirt, I was just cleaning all the time! Just wondering if this is mean or bad for the dogs?????They are spoiled otherwise, trust me!