We have prepared an in-depth blog post covering this topic, check it out here.
In short, it depends on whether carpet is located in a low-traffic area or a high-traffic area. We would suggest repairing the carpet in cases of lumps, carpet burns, set-in stains, low-traffic areas signs of wear. Replacing your carpet is always a good idea, however do expect to pay more. We recommend contacting a professional cleaning company to inspect your carpet before making a decision.