For peace of mind I'd change them. Here's what Michelin recommends:
3. Tires show signs of aging
It is difficult to predict a tire's lifespan because it bears no relation to its manufacturing date. Tires that have never been used, or have only been used infrequently, may still show signs of aging. Many factors can affect their lifespan: weather conditions, storage and usage conditions, load, speed, tire pressure, maintenance, riding style, and so on.
Michelin recommends that all riders regularly spend some time inspecting their tires to pick up on any external signs of aging or wear, such as deformations or cracks in the tread, on the shoulders or sides.
You should also have your tires checked by a professional who can assess if they should be replaced or not.
The 5 year test… before it's too late!
After 5 years or more of use, tires should be examined every year by a professional mechanic. If the tires need to be changed, follow the manufacturer's recommendations with regard to replacing original components. As a precaution, all tires that have not been replaced after ten years should be changed, even if they appear to be in a generally good condition and have not reached their tread wear limit