In Krung Thep Maha Nakhon (Bangkok), there is an award-winning restaurant called Wattana Panich, where you can order and then eat a beef and goat soup that is 49 years old.
The soup, which is described as "delicious and aromatic" as well as having a "real depth of flavor that's hard to explain", has been brewed by three generations of chefs working at the restaurant. Every night, whatever is in the pot gets stored, and brought out again the following day. More ingredients are added, and the whole process starts again, day in, day out, for decades.
In Japan, the restaurant Otafuku in the Asakusa district of Tokyo serves a stew called oden, which has been replenished constantly since 1945. The only reason it doesn't date back until 1916, when the restaurant opened, is said to be because that soup was lost in a World War II air raid. Another soup supposedly lasted from the 15th century until it met its match in World War II too.
As repeat customers, a lack of dead ones, and a range of good Tripadvisor reviews implies, the soups are safe to eat, though we wouldn't recommend making your own at home.
First off, it's not like you're eating chunks of goat from decades ago, some poor kid that met its end in the heady days of disco. Though it may retain traces of the original components, we are definitely in Soup of Theseus territory.
The soups are heated and kept on a rolling simmer regularly, hot enough to kill any bacteria introduced during that day's top-up. As long as no ingredients detrimental to human health are added, and the soup is constantly boiled to temperatures that will kill off harmful bacteria, the soup can be added to and eaten for a long, long time. Maybe one day you'll get a chance to eat a soup that's older than you.