Hi TST,
You can set posts to 100 and download 100 at a time until you get the entire thread regardless of how long it is.
Go into your profile and scroll down next to the bottom and you will see messages 10 if you click on the arrow by the 10 you can go up to the 100 messages to show.
If you do not have page in the line just above the blue screen in the command line right click it and click command bar.
Then you can click page and save as then you can save however many posts you have your display set too in a file on your computer and keep it from now on and read at any time.
Have fun.
God Bless,
"John 5:39 (KJS) Search the scriptures; for in them ye think ye have eternal life: and they are they which testify of me."