As implemented, there is no time-based dampening. But the events are governed by the same hysteresis that prevents the thrashing of flow control state (a separation between the 'active' and 'inactive' thresholds).
So it depends - based on configuration and traffic flow, it has the potential of being quite frequent.
To be honest, I'm not 100% convinced on the necessity of this feature - especially in light of Gordon's recent implementation of queue threshold events. If someone really wanted events on flow control changes, they could be manually configured on a per-queue basis using the new queue threshold event feature.
I'm leaning toward to deferring this, unless there is an overwhelming consensus to add it.