The respondents can still fill in the surveys even when the study is 'not live', if they have access to an active link. The data will be automatically saved, just like when the study is live. 

We recommend to lock the surveys when they are finished to prevent further modifications. This can also be done automatically, by selecting the option 'lock survey if finished' when editing the survey package in the form editor. Locked surveys cannot be accessed by participants.

Read more about managing scheduled surveys.