Kilimanjaro is a volcano that is beleived to be about one million years old. That means the current glacier covered Kilimanjaro for 12,000 years, or about 0.012% of its lifetime. Kilimanjaro has been without a glacier before, and chances are it will be without a glacier again.
I was thinking Mt. K's glacier must be at least 12,000 years old but much older than that; 12,000 years ago was the end of the last ice age. But re-reading the Nat'l Geographic article I found on the web I learn that the oldest ice in the glacier is 12,000 years old. So maybe there wasn't a glacier at that time (there were wild temperature swings in the one or two thousand years following the last ice age). Or maybe the ice in the glacier is only that old because it's been melting from underneath (Mt. Kilimanjaro is a volcano).
At any rate, the next ice age is supposed to be coming in a few tens of thousand of years. One reckons that mountain will have a fresh glacier by then.
By the way, I live on the Ohio River. The terrain here is hilly -- glacial moraine; the Ohio River's course was determined by the ice. A science museum in Clarksville, Indiana, shows a picture of downtown Louisville, Kentucky, with the ice looming above the office towers.