From a New York Times story by Emily Badger and Eve Washington headlined “It’s Boom Times for Santa”:

There’s a narrow window when most American children believe in Santa. It’s around 3, 4, 5 years old. Six to 8 is starting to push it. Which is to say that, for many families, the pandemic nearly ruined the limited opportunity to get that photo with the child sitting on Santa’s lap in complete awe.