Current rating vs duty cycle
Unless such a relationship is given on the datasheet you can't make any assumptions about increasing the current at a low duty cycle.

Many failure modes of electronic devices are accelerated by high temperature, and in those cases it might be acceptable to specify an average power consumption or to allow for higher currents at low duty cycles. However, even if this is possible you still need to understand the thermal characteristics of the device...just saying "low duty cycle" might not be sufficient...the manufacturer may specify a maximum pulse width at that low duty cycle.

Ultimately, only the manufacturer knows why they have specified a particular current limit. It's possible that a device will be destroyed if you exceed the specified current limit by 20% for 100ns. If it's not in the datasheet then we just don't know.