Go to servey "General setting" -> "Publication and access contal" -> . You will find date and time in front of "Expiry date/time" field . Remove it and save. You will be good to go..
Survey Designer and Programmer
"I always suggest to have a group by group display layout and create a seprate group for each question. This will be extra work but you will get flexiblity to create your question by using more than more lime survey question types."