Most nephrologists feel that a central venous line should have never been placed in the first place. Once placed, the patient should also be evaluated for placement of an AV fistula, and when the fistula has matured and is ready to use - generally around 12 weeks, the catheter should be removed.
There are cases where a patient cannot have a fistula placed, and must have a chronic catheter. In these circumstances, there is not a specific or a set time. It is important that the catheter dressing be changed regularly, and that good hygiene and technique be used. Despite this, the catheter may become infected and need to be replaced.