I have noticed that my O'Keefe and Merritt gas cooktop always stays warm. Is that normal? I am thinking of replacing it for a modern gas cooktop which does not seem to have that problem.
Does it have a pilot light? That would explain it.
Yes, that is normal. It is the pilot lights as weissman said.
If your cooktop has a pilot light it's probably produced prior to 1985. I'm pretty sure the O'Keefe & Merrit went to electronic ignition around that time.
Mine does, too. The guy who installed it for me said that some people light the stove pilot lights by hand during the summer, to keep the house cooler.