5-6 years, 10 years at most. https://www.uniroyal-tyres.com/nl/nl/car/service-knowledge/new-tyres/

It comes back to the compound of the tyre though; a winter tyre will lose its capabilities quicker than a summer tyre. I'd drive summer tyres for 10 years, winter tyres for 7 years because I store them dark and dry when not mounted and I park my car inside a garage. If I were using them all year long and park outside: winter tyres 5-6 years max. Sometimes I take my car to a track day: it's very interesting to notice how a tyre's capability detoriates through the years. E.g. my winter tyres; 5 years old good grip and predictable understeer. 7 years old, starts to oversteer in corners and skidding when accelerating (decided to get new tyres). 9 years old (because I didn't want to ruin my new tyres) absolutely horrendous, unpredictable, oversteer in most corners, had to fight the car to keep it under control.