The culture of an organisation does not sustain itself. Left to its own devices culture shifts in unpredictable directions as new people arrive with different backgrounds and others, who were part of it, move on.
In small places were the people don’t change then maybe it can remain fairly constant, but even then people forget things or fall prey to their own fears.
So once you have the culture you want, you must actively maintain it. The most obvious way is to get to the new starters and indoctrinate them early on. That’s why most HR departments keep starters to themselves for hours, or even days, before they let them join their team.
But after that, you have to keep up the work by restating the cultural principles at regular intervals. Doesn’t matter if most people are well aware of what you are going to say because it is those that aren’t familiar with the vision that matter. They are the ones who will subconsciously pull the culture in other directions unless they are made plainly aware of where the current culture is.
Another good move is to spot when something happens that is a powerful embodiment of the culture and highlight that so that even the least clued up person understands the message.
I’m sure there are lots of other techniques, it doesn’t matter. So long as you don’t expect the culture achieved at one time to be the same some time later, without any work. If you think like that then you’ll get a shock one day when you realise that almost everyone else now shares a different culture and you are the only one who didn’t move with them.