My husband worked for Clark’s and he says every 6/8 weeks x
You can measure them at home if you can get LO to stand still on a sheet of paper
I go to a shoe shop and my little one goes back every 12 weeks x
We take our LG to get measured every 6/8 weeks x
In Next you can pick up a print out to measure their feet at home, really handy to get an idea of if you need to go up a size
I recently got my lo remeasured last week and the shoe shop said at the moment every 6-8 weeks