Looking on the internet deeply has found these results:

I will let you know as the date gets closer is the most popular phrase on the web.

I will let you know once i know the date 13 results on the web	I will let you know as the date gets closer 1773 results on the web More popular!
Some examples and use cases from the internet:	Some examples and use cases from the internet:
I will let you know when I have those results. I'll let you know once I solve the case. I'll let you know once it goes down. Thanks, I'll let you know once I made a decision, Nigel. But I will let you know when you cracked the case. I will let you know when it is finished. Once I know I got the 50 grand, I'll let you know where you can find the girl. And I promise that the moment I know anything, anything at all, I will let you know.	I will let you know when it is finished. But I will let you know when you cracked the case. I will let you know if and when we need more guns. I will let you know when I have those results. I will let you know as soon as we find out anything. I will talk it over with my faculty and we will let you know. We have all entrances covered and will let you know as soon as anyone has eyes on the target. I need to take care of this, so I will let you know what I decide.

I will let you know once i know the date

13 results on the web

I will let you know as the date gets closer

1773 results on the web

More popular!

I will let you know when I have those results.
I'll let you know once I solve the case.
I'll let you know once it goes down.
Thanks, I'll let you know once I made a decision, Nigel.
But I will let you know when you cracked the case.
I will let you know when it is finished.
Once I know I got the 50 grand, I'll let you know where you can find the girl.
And I promise that the moment I know anything, anything at all, I will let you know.

I will let you know when it is finished.
But I will let you know when you cracked the case.
I will let you know if and when we need more guns.
I will let you know when I have those results.
I will let you know as soon as we find out anything.
I will talk it over with my faculty and we will let you know.
We have all entrances covered and will let you know as soon as anyone has eyes on the target.
I need to take care of this, so I will let you know what I decide.