A 58-year-old man with type 2 diabetes is reviewed in general practice. He has had diabetes for 8 years and is on metformin and gliclazide with good glycaemic control. His eGFR is 80 mL/min/1.73 m² and urinary albumin-to-creatinine ratio is normal. According to RACGP recommendations, how often should he be screened for diabetic nephropathy?