This is a typical situation most car owner will face.
In my opinion, usually dealer or big franchise garage has higher standard (plus they want to grab more money from you). For example, if there are 50% left on the item, they will ask to change. But in fact such item may be able to run safely with 20% left. This is an example.
On the other hand, if you know a mechanic well, and he will tell you the true story. In general, if the part is original or genuine, it should have longer lifespan/liability than an after-market one.
Car owner need to feel how confident at which level to change the part. If you are not confident, or don't have time to investigate, then change it now. Otherwise, try to find someone or small garage which you could trust and get the truth story.
At the end, it is the owner's responsability to make sure the car is safe. Opinions from others are just opinions, including mine
.