I would strongly argue for CEA bloods ...forever.
Last year, nearly ten years after my original diagnosis my CEA started to rise. Two months later it had risen some more and I was sent for a PET scan. A tumour on my lung and 2 lymph nodes. NSC Lung Cancer.
Without that CEA my NSCLC would have advanced to Stage 4.
For now I owe my life to the CEA test.