For cows we used to drive 8 ft t posts at least 3 feet in the ground. We changed our all wooden fences to t posts around 2002 and have to this day none have needed replacement, unless the fenceline was changed. Also, the way I put clamps on is such that they never come undone unless they rust through, and never move past a notch it was placed between. The fence mesh itself would be the most vulnerable area, breaking when hooves are placed through it, or bending to far up between posts allowing a cows head underneath, sometimes calves get out this way. The lowermost clamp is difficult to properly attach due to the ground being in the way of hands and tools, but the lowest one is the most important and must not be left loose.