Well, the dmin depends on process chemistry and darkroom lighting to some extent. The paper and developer contain optical brighteners which can whiten up paper visually if there is enough or if there is UV illumination. Some kits have no brightener. So, the answer is "it depends". Lack of brightener causes a significant yellowing.

Also, 5 years is not much keeping but that again depends on the conditions. So, one answer does not fit all!

PE