Fuel Injectors on a vehicle usually last a pretty long time and sometimes as long as the vehicle itself.
Usually a vehicles fuel injector system will need cleaned periodically but other than that you should get 10 to 15 years or more out of fuel injectors before needing to replace them.
Fuel Injectors are expected to last at least a billion cycles which is essentially the life of the vehicle.
But sometimes something can happen to cause the fuel injectors to fail sooner such as bad fuel or dirty fuel or debris damaging the fuel injectors.
But you really should not need to replace fuel injectors all that often.