Socks and pants are always fresh on daily.
The rest, when they are dirty. By which I mean smell or look dirty.
For ds, that means trousers and tops after anything from 1-4 wears, as he loves sliding on the floor/grass/mud, but for dd, that may mean a dress, skirt or top gets 5 or 6 or even seven wears before it hits the laundry basket.
Judge away.
dd is 9 and not yet developing, so no sweat to deal with unless she's been exercising hard. I fail to see how clothes can need washing just because they've spent the day being worn rather than being in a drawer. And I can't bear the modern obsession with washing everything all the time. We don't have a dishwasher, tumble dryer, second car, or flying holidays either, so I appreciate we may be a bit weird.
The dc wash daily, so a day pottering around the house really makes no discernible difference to their clothes, as far as I can tell.
I, otoh, sweat like a bugger and put everything on fresh daily, as does dh. But we rarely need to do more than 4 machine washes a week, including coloured/white/delicates, which I think is a lot more eco-friendly.