"Typical" is a relative term, like "normal" :p
But, given the right conditions, with little to no interruptions, I'd say a couple of weeks should be enough time for all possible spawner year classes to do their thing. Perfect conditions, and they could possibly get'r done in a week. But, when & where do "perfect" conditions occur :p It's only a once in a great many years that we have anything close to "normal" conditions, let alone perfect ones :D
You also have to take into account the fact that, if you have both species of Crappie in your lake ... they don't usually spawn at the same time. So, overall, from the first wave to the last (of both species - Black Crappie & White Crappie) ... can be stretched out over a month's time, or possibly longer.
... cp