Looking on the internet deeply has found these results:

couldn't be more grateful for is the most popular phrase on the web.

couldn't be more grateful to 1105,000 results on the web	couldn't be more grateful for 1218,000 results on the web More popular!
Some examples and use cases from the internet:	Some examples and use cases from the internet:
My mistress and I could not be more grateful for the kindness you have shown us. If we have a baby, we'll be more grateful. And I couldn't be more grateful for you letting me camp out, but I... I don't want to overstay my welcome. But not tonight, on a night he'd be more grateful than ever. Like I said, we couldn't be more grateful. Don't get me wrong, I couldn't be more grateful for everything you've done. You think you'd be more grateful to the guy who saved your life at Area 51. I have never been more grateful to be an only child.	Don't get me wrong, I couldn't be more grateful for everything you've done. Like I said, we couldn't be more grateful. If we have a baby, we'll be more grateful. You think you'd be more grateful to the guy who saved your life at Area 51. My mistress and I could not be more grateful for the kindness you have shown us. I should've been more grateful for my Paul. But not tonight, on a night he'd be more grateful than ever. And I couldn't be more grateful for you letting me camp out, but I... I don't want to overstay my welcome.

couldn't be more grateful to

1105,000 results on the web

couldn't be more grateful for

1218,000 results on the web

More popular!

My mistress and I could not be more grateful for the kindness you have shown us.
If we have a baby, we'll be more grateful.
And I couldn't be more grateful for you letting me camp out, but I... I don't want to overstay my welcome.
But not tonight, on a night he'd be more grateful than ever.
Like I said, we couldn't be more grateful.
Don't get me wrong, I couldn't be more grateful for everything you've done.
You think you'd be more grateful to the guy who saved your life at Area 51.
I have never been more grateful to be an only child.

Don't get me wrong, I couldn't be more grateful for everything you've done.
Like I said, we couldn't be more grateful.
If we have a baby, we'll be more grateful.
You think you'd be more grateful to the guy who saved your life at Area 51.
My mistress and I could not be more grateful for the kindness you have shown us.
I should've been more grateful for my Paul.
But not tonight, on a night he'd be more grateful than ever.
And I couldn't be more grateful for you letting me camp out, but I... I don't want to overstay my welcome.