Looking on the internet deeply has found these results:

I would like to thank you for dedicating part of your time to write the letters. is the most popular phrase on the web.

I would like to thank you for devoting part of your time to writing the letters. 148,200,000 results on the web	I would like to thank you for dedicating part of your time to write the letters. 1168,000,000 results on the web More popular!
Some examples and use cases from the internet:	Some examples and use cases from the internet:
Mr President, I would like to thank you all for a good, comprehensive debate. I would like to thank you all for coming today. Mr President, I would like to thank you all for this long but stimulating debate. Anyhow, I would like to thank you But... I would like to thank you and clear up a misunderstanding. I would like to thank you for your comments, Mr Stenmarck. Ladies and gentlemen, I would like to thank you for your speeches. I would like to thank you for your understanding.	I would like to thank you and clear up a misunderstanding. Mr President, I would like to thank you all for this long but stimulating debate. I would like to thank you for your understanding. I would like to thank you for your comments, Mr Stenmarck. Mr President, I would like to thank you all for a good, comprehensive debate. Ladies and gentlemen, I would like to thank you for your speeches. Anyhow, I would like to thank you But... I would like to thank you all for coming today.

I would like to thank you for devoting part of your time to writing the letters.

148,200,000 results on the web

I would like to thank you for dedicating part of your time to write the letters.

1168,000,000 results on the web

More popular!

Mr President, I would like to thank you all for a good, comprehensive debate.
I would like to thank you all for coming today.
Mr President, I would like to thank you all for this long but stimulating debate.
Anyhow, I would like to thank you But...
I would like to thank you and clear up a misunderstanding.
I would like to thank you for your comments, Mr Stenmarck.
Ladies and gentlemen, I would like to thank you for your speeches.
I would like to thank you for your understanding.

I would like to thank you and clear up a misunderstanding.
Mr President, I would like to thank you all for this long but stimulating debate.
I would like to thank you for your understanding.
I would like to thank you for your comments, Mr Stenmarck.
Mr President, I would like to thank you all for a good, comprehensive debate.
Ladies and gentlemen, I would like to thank you for your speeches.
Anyhow, I would like to thank you But...
I would like to thank you all for coming today.