Stale bread is something quite rare in my kitchen. I usually bake one sourdough loaf once per week and eat it in the next three or four days (OK, sometimes in three hours). After four days your sourdough bread has probably lost most of its crunchiness but there is solution for that - make croutons and mix them in a soup afterwards. The aroma of toasted slices will give a nice nutty tinge to your soup and then you will start making croutons out of fresh bread. Like I did and do.