The COS-B mission lasted about 6.8 years and during this time the sensitivity of the experiment and the instrumental background varied due to several effects. Many of these effects have been taken into account when deriving the final database others remain embedded within it. Since the timescales of these effects, ranging from hours to years, only allowed a partial correction, this chapter is included to avoid the user being misled by temporal or other artifacts in the data when searching for time variability of gamma-ray sources, or intensities in regions of weak emission or at large incidence angles relative to the telescope axis.