If you log in on the page that farmhelper takes you to there is not checkbox option to stay logged in. Instead click on the facebook logo in the upper left corner (under the new refresh button) and log in on the page that comes up and check the stay logged in button. Next time you open farmhelper you will be logged in.

You can also login first in your web browser and choose the keep logged in option. It will save it for the bot that way as well.

I tried that and it does not help. I logged onto IE facebook and checked keep me checked in. After that I run the program. It logges on but then it logs off again.