One of the most important features for any survey is to have a “save and continue later” button. This is important especially if the survey is long. When the survey is longer than 2-3 pages, sometimes users will complete part of the survey and will want to come back to the rest at a later date. When the respondents do come back at a later date, they will see the responses that they completed the last time they were taking the survey and will be able to start where they left off.
Watch this video tutorial for more information: