Here’s your cheat sheet. Brown lentils: 25 minutes. Red lentils: 15 minutes. Green lentils: 35 minutes. Any lentil left unattended with a glass of wine: potentially 2 hours (you were having fun).
But seriously, the best way to know when they’re done is to trust your tongue. Don’t overthink it. Lentils are forgiving little guys. They want you to eat well.
So go on. Open that bag. Rinse them. Boil them. And if all else fails, just cook them until you get hungry enough to stop waiting. That’s the real secret.