Longitudinal study designs are scientifically, socially, and culturally meaningful and of value because their findings show people’s life trajectories honestly. The meaning and value would be getting greater and greater if the older adults were participants for the longitudinal study. The main reason for that is because the inter-individual variations would be getting bigger owing to the greater environmental influences in the second half of life and the variations can be uncovered only through repeated observations of individuals on the temporal dimension. Although it is not easy to carry out the longitudinal study in reality due to consuming time and money too much, we should understand its scientific and social value as well as its meaning in the future.