The rule of the thumb: How long should tyres last?

There are no statutory prescriptions on how long a tyre might last. The only exception is: tyres for trailers that have a special permit for a maximum speed of 60 mph may be no older than six years. In all other cases, it is up to the driver to decide when the tyres have exceeded their lifespan. Nevertheless, the road traffic regulations stipulate very clearly that a car with all its equipment must be roadworthy at all times. That, of course, includes the tyres.
There are a few criteria that will help you to decide if you can keep using your tyres and when you should replace them. As a guide, the following applies: You drive with four similar tyres, each of which has a tread depth of at least 3 mm for summer tyres or 4 mm for winter tyres, and are no more than ten years old.
If you keep this in mind, you will be safe. At the same time, you will have a sufficient margin of time to look after replacing the tyres when they are coming closer to the threshold. That is because the minimum tread depth prescribed by law is 1.6 mm, well below the recommended threshold.

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Good to know: Tyre lifespan

The age of the tyres speaks much about their roadworthiness. What’s more, it has nothing to do with their mileage and wear: over the years, the rubber in the tyres will become more brittle, braking distances will become longer and the traction that ensures better performance on slippery surfaces will also deteriorate. However, adequate road grip and traction, particularly when driving in snow during the winter or on wet roads, is vitally important.
Studies clearly demonstrate, for example, that summer tyres become less safe over the years – and that was despite all tested tyres having a tread depth of at least 5 mm. However, this impairs braking performance. This occurs primarily in wet conditions and with aquaplaning, but performance on dry roads is also affected. A further aspect concerns technical advancements. The older a tyre is, the less it conforms to ever-advancing safety standards.
While there are indeed no precise statutory requirements as to how old a car tyre may be, sensible indicators do exist that you can use as a guide. What you should know: you can work out the tyre age for yourself, using one of the codes moulded on the tyre. We will now talk about the tyre age at which you should replace your tyres. One more tip for when you buy a used car: if you want to be on the safe side and not have an unpleasant surprise later on, do get confirmation of the age of the tyres at the time of purchase.

 
Tyre age: Old DOT numbers

If you find only three digits and a small triangle on the sidewalls of the tyre, then the first two digits indicate the calendar week and the last digit indicates the year in the 1990 to 1999 period. If there is no triangle, then the tyre is from the 1980s at the latest, and you should purchase new tyres at the earliest opportunity.
 
Tyre wear: What can you do about it?

Aside from age, there are many other factors that affect how long tyres last. One factor, for example, involves kerbstones, weathering, collisions with objects or incorrect vehicle settings. As the owner of your car, you can do some things yourself to ensure that your tyres have a long lifespan. Check the tread surface and sidewalls of your tyres regularly.
You can, for example, test the wheel alignment yourself by taking your hands off the steering wheel while travelling at about 35 to 50 mph on a road that is as level as possible and has little traffic: if the car veers noticeably to one side, you should have it checked at a garage and get it readjusted.
If there is poor balancing, excessively low tyre pressure or worn-out shock absorbers, you can take the appropriate measures to address these problems. That way you can extend the lifespan of your tyres and avoid having to replace your tyres early.

Proper storage: How to store your tyres
The storage itself will also affect how long the tyres will last. To prevent premature ageing of the tyres, make sure they are protected from UV light. If possible, store the tyres in a cool, dry and dark place.
Important: Make sure that the tyres do not come into contact with solvents, lubricants or chemicals. Do not store tyres in the same place as equipment that produces ozone (for example, electrical generators or electric motors used in compressors). That is because over time, ozone is harmful to the rubber compound in the tyres. If no suitable storage space is available, you can also have the tyres stored at a garage.

Source: Uniroyal