If the Pprune does not detect any movement, it logs you out, I think, in about half an hour. However, if you have the "remember me" cookie, it will log you back in but only after you've lost what you've typed.
As said, type into Word and copy/paste (the font is Verdana 10 - indigo) or learn to touch type quickly like wot I do!!!
Cheers
Whirls