When people ask how long does uPVC double glazing last, the short answer is a minimum of 20 years. However, this depends on a series of factors so there really is no accurate response. It’s like estimating the lifespan of a timber fence, a gearbox or a pair of jeans.
Two people buying the same make and model of car won’t get exactly the same longevity out of the vehicle. If one person lives near the coast and drives 30 miles a day, doesn’t get it regularly serviced or wash it frequently, while the other only drives 5 miles a day, lives in an unexposed area, gets regular services and takes great pride in the appearance of their car, then the results will likely be vastly different.