Pulsed drain current, max. rating

In the Maximum Ratings table, the datasheets mention the I_D pulsed.

Take the EPC2012C datasheet for example. For T_PULSE=300us, I_D=22A. What I find missing in the datasheet is the pulse duty cycle. I assume T_PULSE is the period. What is the maximum duty cycle allowed for the drain current of 22A?

the pulsed rating is used to specify that the device can carry this current. In particular this is a max rating so it means that we take care that all devices produced will be able to carry this current without saturating. However it is no intended as a thermal limit. The pulse needs to be limited to make sure Tj stays below Tjmax (°C). This can be done by calculating losses and using the thermal impedance curves.
Figure 12 (SOA) already does this calculation for a few pulse conditions (100µs, 1ms, 10ms,100ms).