It only takes ~5 minutes per day. My girlfriend has well over 1000 days. I got ill at some point, forgot my streak freeze, and had to give up at around 500 or so. Then I lost interest... I did miss the whole update where they started with advertisements to pay for the application (which are akin to spam because apparently 'no' does not mean 'no'). I'd have quit over that regardless. Though perhaps a webbrowser or PWA would do the trick (I use the Android version).

That being said, I did learn quite some Spanish and I'm happy I did but I am not sure Duolingo (or Memrise for that matter which I also tried) works better than high school spaced repetition, Anki, or Pimsleur.