Hi, Htlaps,
I think your face and expression drawings are completely but totally expressive but solid, in terms of them being done for 60 seconds each, but I feel that these faces and expressions all seem too rigid to me yet. How would you like to please go for 16 minutes of 30 second faces and expressions sketches, all just to completely and totally loosen up your forces and forms of those faces?
The reason why is because, your accuracy and speed will constantly improve with much more constant practice, even if you're past 10 hours of drawing practice or more, but to make your facial forms and forces less rigider, but all the most spontaneous, fluider, but more human yet.
For most info, look into the Andrew Loomis book on Drawing Faces and Hands, for more practice on drawing faces and more, so hope these have helped you out the most.
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