Epson LQ-860 User Manual page 27

Film ribbon cartridges must be used and
CAUTION:
stored within the following temperature ranges:
Operation: 60° F to 95° F (15° C to 35° C)
Storage: -22° F to 104° F (-30° C to 40° C)
Storing and using a film ribbon at high temperatures
shortens the ribbon's life expectancy, which is normally
100,000 characters (#7764). Film ribbon prints in red near
the end of the ribbon. Replace the film ribbon at this point.
If you continue to use the ribbon beyond its life
expectancy, printing suddenly becomes faint and the
ribbon may snap.
Setting Up the Printer 1-13