Sheep live between 10 and 12 years in the wild. The longest-lived sheep in the world, according to Guinness World Records, was a Merino sheep who was 23 when she died.
Sheep that are raised for slaughter are typically killed between the ages of 1 and 2 years because their flesh is most tender then. Sheep kept in herds are often culled after the age of 7 because their health and wool generally decline at that point. Older sheep have worn teeth, so it is harder for them to feed themselves and graze in short grass. Older sheep also have a more difficult time providing quality milk for their ewes.