Ball valves are some of the easiest valves to use in pipes, and their shape and typical operation make them among the more durable as well. Yet they're not completely immune to any damage; in fact, some damage can be quite common. Most of this damage is completely preventable, requiring only some preparation and care. With those safeguards in place, the ball valves you use can last a much longer time.
When you shut off a ball valve, you turn the ball so that the entrance and exit areas are now blocked. Unfortunately, that means fluid can be trapped inside the ball. If that fluid can freeze, you can end up with trapped ice when the temperature outside the valve drops below freezing. Ice expands, and if you've ever dealt with potholes in asphalt after cold weather, you know the rest. The ice expands, cracking or warping parts of the valve. This is easily solved by adding insulation around the valve or using valve parts made for very cold weather that prevent freezing.
On the opposite side of the temperature range is excessive heat, either air temperature or fluid temperature. If the ball valve isn't lined or insulated, or you use a valve that has a temperature limit below what it's exposed to, you can encounter softening, and even melting. Ensure the valves are all appropriately rated for the type of fluid you're using, and try to shade or enclose the valve to protect it from hot weather.
Too Much Force
If the valve is a manual one, where a human has to turn it on and off, ensure that human isn't using too much force. Jamming a valve handle to one side or the other can break it, like it can break any other handle, switch, or knob. If the valve has a lot of resistance, you've got to inspect it and ensure it's not getting caught on something and not fighting against fluid pressure that's too great to overcome.
Wear and Corrosion
The usual suspects for a lot of equipment are simple wear and corrosion. These can be reduced by regularly inspecting the valve, cleaning the area it's in, and so on.
Most ball valves do need eventual replacement like any piece of equipment, so your goal is to extend the valve's life for as long as possible. If you have to replace it, look for ones that are slightly tougher than you think you need to get just a little more protection.