For us it was around 8/9.
We give a main gift, some surprises and smaller bits in a stocking.
Until 8/9 the main gift wasn’t too expensive. It was often something daft, imaginary or impractical. Often something they had set their heart on but would have very little play value or be a disappointment on the day I’m looking at you stupid flying fairy
So it made sense to me to pick out a few gifts that would suit them well and bring them as surprises.
But around 8/9 they started hankering after more expensive things for the main gift, but they were still very attached to the idea of their surprises (which were always the best part). I fully intended being firm about it and saying that they could ask Santa for X but it was a big gift so they wouldn’t get as many small surprises but they weren’t really mature enough yet.
Other dc might be. My eldest has asd so it complicates these things a bit as he was going through these dilemmas first. I could also see a situation where, as the eldest, he’d always have a smaller pile than dd, because his desires and needs would change and I’m not sure that’s fair either.
Anyway, long story short, we increased our Christmas budget, and expect to do so again as teenagers.
The pile isn’t huge; maybe 4-6 well chosen things that are always used. Sometimes I feel I should have just done main gifts and stockings but I think there were good reasons not to. Maybe if I was starting again, I’d eliminate the main gift and encourage them to expect a surprise but once they get to school, they are exposed to the idea of asking for something.
I do still enforce some budgetary constraints of course, and by MN standards I’m positively mean. We also have a policy of not giving tech gifts (so far) as we wanted to be very clear on screen limits and privileges. They have access to tech but not ownership at this point. So I’m not even counting what we have spent on iPads etc.
We don’t do a huge amount of activities as ds can’t handle it. We see a cheapish but amazing Santa, and I take dd to a show, and ice skating every week. But it can be very expensive if you do a lot of activities and santa experiences and that starts young.