Why is it important to know the duty cycle of the mode you are using when transmitting?
Why Duty cycle is the fraction of time a transmitter is putting out full power during a transmission, and it determines the average power the final amplifier, power supply and antenna components must dissipate as heat. SSB voice has a low duty cycle (roughly 20-25 percent) because power only peaks on voice syllables, while FM, RTTY, and digital modes like FT8 key the transmitter at full output continuously, a 100 percent duty cycle. Running a continuous-carrier mode at the same power setting you use for SSB can overheat the finals and exceed the rig's average power rating, so many manuals tell you to reduce power for those modes.
Watch out Overmodulation is an audio drive level problem, not a thermal one, and tuning or listening for break-in calls has nothing to do with how long the carrier is present.
Duty cycle = heat. FM/RTTY/FT8 are 100 percent on; back the power down or cook the finals.