People back in the day could usually live a pretty long time if they were both rich and lived past a certain age. Ramses lived to his 80s and Menes was gored to death by a Hippo also at around the 80s. Antigonos died in battle close to his 80s.

But by looking at some of the famous figures in the Late Republic and early Empire, you could probably estimate somewhere in the late 50s early 60s if you include non-natural deaths.