I made chili and it's too hot! If I cook it longer will the heat calm down?
Acids tend to reduce the heat of chilli, so you could try adding some vinegar or lime juice. If that makes the dish too acidic, add some sugar to balance it out. Dairy also reduces the heat so you could serve with sour cream and/or cheese, or even stir some butter into the chilli, which would also give it a slightly richer taste.
No cooking it longer will make it worse. In my experience chili stays the same or gets hotter with age. If your Chili is too hot the best thing to do is make another batch without the chili or Tabasco or the heat ingredient/s you used and then mix the two batches together but failing making a new batch serve it with a dairy product like melted cheese or plain yoghurt. The proteins from the milk attach to the chili heat and coat them so your mouth is protected from the heat. Also sweet and vinegar based accompaniments will also reduce the heat a little but the best are milk products or you can drink milk while eating it to cut the heat in your mouth. But be warned it only cuts the heat in your mouth and what goes in must come out if you know what I mean.
I added an undiluted can of tomato soup but the real saviour was butter which immediately calmed the whole dutch oven batch to a really great tasting chili. I probably stirred in a good 2 tblsp. Finally, if serving in bowls, as I didn't have sour cream, I did a little spiral of ranch dressing on top. GREAT !