I have the 20 oz cups with the closing lids. If the slide on the lid is kept closed it will keep ice for 24 hours. If the slide lid is left open ice won't last as long. Adding cold drinks doesn't melt the ice away. Sunday morning I filled it with coffee at 7 am, refilled/emptied the pot at 8:30 am. It was still hot at 8 pm. Poured out about 6 oz.