Thanks for confirming this although it's not what I had hoped ☺
For your info: Hilton, Marriott, Wyndham, American Airlines all state that earning or redeeming extends the expiration date

Last year my expiration date changed when other points, not related to a stay, posted. It seems a stay is not really necessary.
I was hoping to use part of my points for a stay after the expiration date but it seems that this would mean I would loose the remaining balance. Will need to look into alternatives...

There are many airlines for which any activity, including burning, prolongs the life of miles.
That is the case for BA, IB or for AA, for instance.
In relation to hotel chains, it is also the case with IHG that any activity, including burning, resets the clock. Ditto for Radisson. [and Marriott Bonvoy too, as confirmed by kcaluwae].

Thank you guys. We learn things everyday on FT ^
But I have to say, I find this a bit weird from the company perspective. But for the customer, it is for sure good. :)

I went through the history of my stays and it seems that Accor points are posted on the check-out date. Is it safe to assume that a stay 2 or 3 days before the expiration date will be OK to extend the expiration date and keep your points?

stay on the safe side !
it takes sometimes 7 days before the processed it on your account always the checkout date
so 2 weeks before is wise
greetings cornelis

You should inform the hotel when checking out that you need the points to be posted very quickly. Otherwise, you are at risk.

The TandCs explicitly state that the valid date for the 365 days period expiration purposes is the check-out date. You may have to ask for your points to be re-instated if the hotel is slow to post and Accor very quick to wipe out but I cannot see how they could possibly refuse reinstating given that the TandCs are crystal clear that the relevant date is the check-out date (rather than the posting date).