Best solution here - remember 'Copy then Post'.
I tried this but the formatting usually gets lost. But if I am in the middle of a lengthy post and get timed out, I sometimes lose the text.

Best to keep posts short and to the point. 
I've sometimes had to go right back to the thread and start again with a Reply or Quote. Copying has saved me lots of time - but then I ramble in wordy posts, as you know! ;)
I just highlight everything in the grey box, use the browser's 'Copy' then click anywhere in the grey box to remove the highlighting, then Post.
If it chugs along and freezes, I can usually not Post again without reloading the page, but then all I have to do is Paste and then Post.
I use Firefox, but I've found the same on Chrome, Explorer etc.