My advice, based on what I've seen to date:
1) All patients on super-tight-control diabetes programs (especially type 2 patients) where A1C is being forced below 6.0 should be reassessed for cardiovascular disease by their physicians. And if there's evidence of heart or blood vessel disease, and/or hypertension and/or hyperlipidemia, the level of control might be loosened to allow the A1C to float up to 7.0 or perhaps slightly higher. And if not already on aspirin and other preventative tools for cardiovascular disease (such as smoking cessation), such tools should probably be started.
2) All patients with type 2 diabetes and A1C below 6.0 and known heart or other cardiovascular disease should have their diabetes program rechecked -- and if they are prone to hypoglycemia, the level of control should probably be loosened to allow the A1C to float up to 7.0 or higher. And maybe even if not prone to hypoglycemia, the control should be loosened.
3) And anyone with diabetes whose A1C is still 8.0 or above should continue to work to lower the A1C to the range of 7.0-7.9, and perhaps lower, and should be under the care and close supervision of a highly-skilled diabetes team. After all, it's very clear that blood sugar control reduces complications resulting from diabetes including eye, kidney, and nervous system diseases in people with both type 1 and type 2 diabetes.
