You can register as a teacher and create your own classroom to get unlimited hearts forever for free.

I think when they originally started with Hearts A/B testing (really long time ago, can’t remember when) I wasn’t even able to refill my hearts without using gems. Don’t think there was any other way to get them back.

Made me quit duolingo for a couple of years.

Thanks for your options and opinions. The streak is addictive but I decided to punish this move by Duolingo and delete the app. I switched to LingoDeer for now. I did find this fun message when I tried to delete the app that made me chuckle.