Our Crockpot ("the original slow cooker") is programable with High settings for 4 and 8 hours, and Low settings (8 hours and another- I haven't gone to the kitchen and looked).
The High is a slow boil.
Other models, my daughter's, has a high and low setting, but no timer.
Ours is several years old and works well.

At our ages (90 and 89) we don't do chickens from scratch any more. We usually get a baked (barbecued?) one at the market and when the best meat is gone, the carcase goes into the pot and is boiled until the meat is ready to fall off. It is stripped and then the meat is made up into stew, soup, with spices, rice and vegetables or whatever. We don't bother with the crockpot for this.

But we often buy quick meals, M&M or the many kinds available in our markets so all we have to do is heat and serve.These may have the extra ingredients (preservatives, etc.) that gnu mentions, but the convenience is paramount.

The Crockpot is used to make out chili, which takes time, but it is something we can't do without. None of the prepared chili con carne con frijoles in the markets is edible.