I just cancelled my Super Duolingo subscription and let my 759 day streak end. Not because I’m abandoning my learning but because I had noticed that I had stopped really learning in the interest of maintaining my streak and other gamification perks. I was avoiding difficult “assignments”, rushing through lessons, etc… I am still doing a daily practice but I keep track myself and focus on doing a good job, not earning whatever perk is being offered up.
I think gamification can have real value for teaching and learning, but there is always the risk that it becomes more about the “game” than the learning.