Extra long sentences in timed practice
In several of the French modules (for example the Modal Verbs one) the sentences used tend to be very long. This can be a problem with timed practice: if you have 30 seconds for the entire practice session, and a third of that is spent listening to "the voice" reciting the first sentence, your chances of finishing the exercise are close to zero. How about removing the longer sentences from timed practice? Better yet, how about removing sentences that are nothing more than a long list of, for example, names of colours.
It seems this problem is actually addressed - though not perfectly. It seems that one dose get more short sentences in timed practice, but occasionally these monsters of sentences do show up. A better solution IMO is if one would get time to finish each sentence based on the length of the sentence.
I have seen a few occasions where a longer sentence (in Italian) yields 10 seconds instead of 7, so I think Duolingo has some recognition of this as a problem. Doesn't help much for the first such sentence (especially if it appears mid-test), but if there's several in a row...
Perhaps there could be a way of collecting data on each user's typing speed, and altering the points awarded based on how long it would have taken you to type the sentence? This would have the additional benefits, of making timed practice more accessible for slow typers, and ensuring that fast typers were rewarded for their language acquisition rather than their typing speed.