The Michelin Man web address statement makes the most sense to me:
Do I need new tires? | When to change tires | Michelin US
Here's what it says:
What are the basics?
There is no way to tell exactly how long a tire lasts. The lifespan and mileage of a tire depends of a combination of factors: its design, the driver’s habits, the climate, the road conditions and the care that's put into the tires.
A few milestones and tips:
1- Keep five years in mind
After five years or more in use, your tires should be thoroughly inspected at least once per year by a professional.
2- Ten years is a maximum
If the tires haven't been replaced 10 years after their date of manufacture, as a precaution, Michelin recommends replacing them with new tires. Even if they appear to be in usable condition and have not worn down to the tread wear indicator.
This applies to spare tires as well.
3- Proper care expands a tire’s lifespan
You can increase your tire's longevity by maintaining the correct air pressure, performing regular tire rotations and vehicle maintenance.
Check our Scheduled care tips
For original equipment: follow the vehicle manufacturer’s tire replacement recommendations.