Best storage practices would be in a clean, dark, dry area at (~ 23°C / 72°F) or below. Exposure to UV will break down pigments and cause loss of contrast and saturation.
Color Test Charts
Such as X-Rite colorcheckers. Certified to last two years if stored properly. You can use a spectrophotometer to generate a reference file for an older/faded chart.
Color LVT Film
The main factors affecting the films are humidity and UV light.
If the chart is used heavily (exposed to light every day) it can last up to one year.
If they are stored dark place and not used very often they can last up to 5 years.
Significant heat exposure ( > 52°C / 125°F) will decouple the dyes and significantly hasten the fading time.