Our SNAPL paper [http://cs.brown.edu/~sk/Publications/Papers/Published/pkf-te...] has data on how long students spend. It turns out relatively few hours for pretty high levels of attainment (i.e., of finding the languages).

But as @justinpombrio says, this is also tied to a particular pedagogy. The day after the homework is due, in class, we:

- collectively build up a classifier (programs that tell the languages apart)

- present the intended theory (our ground truth of what is going on)

and then spend the remaining time (30+ minutes) talking about which languages did those particular things, and — most importantly — why those languages did that, especially for the "weird" behaviors. There were often very good reasons for doing so, when viewed in a historical context. In this regard, I'm very much a historicist in the Kuhnian sense.