I'm not aware that there is any requirement to keep them informed. I'm not aware you even need to tell someone that they are an executor, although it's clearly a good idea and polite to let them know.
Barmaid usually knows about these things
I've not even told the executors of my will that I've named them as such (but, as they're the main beneficiaries, it probably won't come as any great surprise to them!).
There's never any requirement to tell someone that they're named as an executor (or, indeed, that they're not) because a will has no legal status until after you're dead anyway.
Be careful. I have heard of someone who wrote several wills without destroying all previous ones, or stating clearly in the last will that it WAS the last will. It was all such a muddle that this person was eventually declared intestate.
You must ensure that all previous wills are destroyed, and that any solicitors holding copies of older wills are instructed to destroy them, too.
As has been said already, there is no requirement to inform anyone that you have designated them as executor.
That did surprise me, but as I am in the process of making my will(Scottish Law) I have landed my sister with the problem. She is getting all the cash so she can have all the aggro.