Styles is playing a record 12 nights at Wembley stadium and 30 at Madison Square Garden, as demand for big artists soars – and audience expectation along with itSelling out a venue such as London’s O2 Arena used to be considered a high point of an artist’s career. Now, selling out just one night there might seem a bit underwhelming. Raye and Olivia Dean will play six nights apiece at the 20,000-capacity hall this year; Dave is playing four, Ariana Grande is playing a whopping 10. Harry Styles, never one to be outdone, last month announced a staggering 30 dates at New York’s Madison Square Garden, with more than 11 million people applying for presale access, as well as a record-breaking 12 nights at Wembley stadium: the most on a single leg of a tour. Taylor Swift managed a mere eight.Swift’s Eras tour, which made more than $2bn (£1.6bn), doesn’t seem a complete outlier any more: Coldplay’s Music of the Spheres tour has lasted four years and made $1.5bn, and the Weeknd’s After Hours Til...