You be best to take the front end apart, replace plug with grease fitting, fill with grease, replace fitting with plug and reassemble. Do this once a year if you wheel and have bigger tires on the axle. Do it every other year depending how much you drive on the street. It like changing your diff fluids, its a maintenance requirement but the how you drive your Jeep that makes up the time interval.
Over time, you will be required to change out the ball joint.
By taking apart your front end, you can also inspect other components as well; ie steering tres, brake pades, caliper movement, shock, brake line, unit bearing, ujoint/yoke, axle splines, and the knuckle itself for cracks.
As the newer vehicles were developed, a lot of the interval maintenance requirements were changed due to the 'inconvenience' of owning a vehicle. Older vehicles (70s) required maintenance every 6 months. Today's vehicles it can be every 5 yrs (or when the computer tells you). The vehicle mfrs basically took away owning/operating a vehicle from the owner's garage to a service garage.
