Experience shows that if the tie rod joint on the left side slackens, the brother on the right side will soon be on the road too. Therefore it may be worthwhile to replace it even though it "still looks good": If you don't do the work yourself, you have to go to the workshop, the steering has to be adjusted and measured and if there is play in the steering again 3 months later it is better to do both joints at the same time.
Typical cases in which replacement is recommended in pairs or sets are brake pads, shock absorbers, tie rod joints and chassis rubbers.
For many items in our shop, an order amount is suggested that relates to the amount required for the entire vehicle.