Surveys can work in various ways. There are surveys that offer points for partial completions (meaning that you don't need to finish the entire survey, can get disqualified and still earn points), while others require a full completion. Also, some require unlimited completions daily, while others allow only one completion a day.
Before you begin a survey, you will see the number of points promised for completing the survey. Points are usually awarded between 1-20 minutes after you complete the survey.
TapResearch and TheoremReach are examples of surveys that award points for partial completions.
YourSurveys is an example of a survey router that allows unlimited completions daily and pays 1000 points per completion.