As with price, the answer is that it depends.
A high-quality automatic gate will last between 10 and 20 years if it is correctly maintained and serviced. Periodic preventative maintenance is a significant factor in your gate’s longevity.
Cleaning and lubricating your gate on a regular basis will go a long way to keeping it in good shape.
Inspecting it for rust or other damage will ensure that you correct issues in a timely manner.
Remove insects and other pests on a regular basis, as even the moisture from slugs can damage a circuit board.
Removing leaves, dirt and other debris from the track and controls can be a big factor.
You can learn more about maintenance here.