DS's room is opposite ours and in line of sight and we slept with both our doors open for the first 12 months. We have started closing them now and using a monitor because we are currently using our air cond and our cat, who for some reason really likes DS, was going into his room and bringing him presents that she had caught around the house at night. Mainly spiders amd geckos and on one memorable time when DH did not close her cat flap for the night, a rat.
DS does not mind at all and is a heavy sleeper. I am glad because it means when he goes into a bed he will be used to his door being shut and won't be able to wander at night.