how long lentils need to cook really depends on the type and their age. Hard to know how long they've been in storage before you bought them, or even before they were packaged. I'm all for continuing to cook them this time, but next time you might cook them in water before adding the rest of the soup ingredients. That's often how lentils are prepared in indian cooking. Also, when you cook pulses, don't add salt until after they're soft. Somehow the salt keeps them from getting soft. You can, however, as a pinch of baking soda as they cook to help soften them. Works well with beans, can't see any reason it wouldn't work with lentils if they were particularly troublesome.

My wife always soak the lentil in water for few hours before start cooking .Yesterday her friend gave a very good lentil soup recipe see the hand written recipe will post to food52 recipe section soon with photos. http://picasaweb.google.com/paulvj0/LentilSoup#slideshow/5541812278018499986

Do you have enough liquid to cook further? If so, continue cooking.

Keep cooking. If your lentils were older, they'd take longer.

Thank you!!! I hated the thought of dumping the entire thing. It has wonderful veggies in it and I'm at a total loss about these lentils. I will continue to let it simmer and see what happens. The soup is a gift for tomorrow so having it today is not important......it just frustrates me that it's so delicious except for the lentils!!!

I don't know if there's anything wrong with the lentils, but they probably will soften more the longer they sit in liquid. I think I would let them continue to cook. The soup will still be good tomorrow if you have to make something else today.