I still get a stocking if we're at my mum's for Christmas and I haven't believed in 40+ years!
I think it's awkward to create a situation where DC must pretend to believe so they get a stocking.
I really think adults overthink the make-believe element of Santa and it gets them into all sorts of trouble such as making up elaborate lies for DC and getting upset when they no longer believe.
I think it would be much better if we all follow the example of our DC and their richly incentive make-believe games. It's really irrelevant whether they actually believe they are an astronaut or a dinosaur or whatever when they're absorbed in a make believe game, they enjoy the magic of it anyway.
The magic of Santa is it's a lovely make-believe game we all play together. We can continue playing this game together long after DC come to understand it's just a game.
I worked out Father Christmas wasn't real when I was pretty young - about Year 1. If you'd asked me any day if the year other than Christmas Eve or Christmas Day if Santa was real, I'd have known the answer was no. (Although I may not have admitted it).
But come Christmas Eve, some doubt would creep into my head and I wasn't sure! I remember trying to stay up all night to prove to myself it was my parents (never managed it!)
And come Christmas morning when the stocking had appeared I got swept up in the magic of it all and just enjoyed it. Santa felt real then, even if I didn't always believe, as I was a child and the boundaries between fantasy and reality were much more blurred than they are in adult-world.
Father Christmas is a lovely game that we should play with our DC as long as they want to play it, not dependent on whether they believe IMO.