My dc stopped believing at 5 and 6, but they still enjoyed playing along for a good few years with a bit of a nudge and a wink.
I think that anticipation of what slip up Santa might have, and what mischief the reindeer would get up to, added a lot to the fun and made it about more than a pile of presents.
And it eased the transition between believing in Santa and knowing but not yet being to old/cool for it.
For a while my two both thought the other still believed, and they played along for each other’s sakes. And they loved seeing mum have a conniption because of the mess Santa made, or shushing me in the queue to see him and begging me not to give out when we got inside. I always pretended to be a bit dazed and struck dumb, and I’d only remember on the way home that I had been going to give him a piece of my mind.
It’s been more of a live theatre experience in our house. This is our first year with everyone fully aware that no one believes and it will be interesting to see how it evolves. But it certainly hasn’t been about lying to them, and then them being crushed and devastated. When they came to me with their suspicions and explained logically why they didn’t believe, I listened and complimented them on their deductive reasoning and initiated them into the Big Secret so they could be part of sharing the magic with others.
I understand why other people don’t want to lie, and I can respect that. And in all honesty, if I had a do-over I might go down that route too. In our social circle Santa was taken for granted and from the time they went to pre school, they were being told about him by lots of people so it might have been more unsettling for them to feel every other adult in their life was either deluded or lying. So it was definitely easier to go with the flow. In a more diverse community I don’t know what I would choose.
But it can definitely be a bit more nuanced than just lying or desperately gaslighting children for one more year of magic. I’ve personally enjoyed the post-Santa period more because I haven’t worried about slipping up but we have still had a lot of fun with it.