Some fence posts can be sitting too shallow on unstable soil which will cause them to be easily damaged. For the post to avoid issues such as tilting or shifting, we recommend setting them 3-4feet below to make them more stable.
We also recommend using a heavy-gauge post. Usually, we use a CS20 instead of a 16-gauge post. A heavier post can resist bending better from the reaction of the concrete around it, or when the wind is too strong.
Posts also need to be thick enough to withstand some damage at the bottom and not buckle or bend. For example, a flag pole has a bigger, wider bottom to make it more resistant to bending due to strong winds.
It is also important to consider the right size of the hole for a post. For example, a 3-inch diameter post should have a 9-inch diameter hole; a 2-inch post, a 6-inch diameter hole, and a 4-inch diameter post should be put in a 12-inch diameter hole so they can hold through the concrete better.