To ensure that you have a reasonable expectation of how long a study will take, you'll see two key figures before you start a study. These are Estimated Completion Time and Maximum Time.
Estimated Completion Time for a study is the approximate time it should take you to complete the study, this is specified by the researcher.
Maximum Time for each study is set by Prolific, which is based on the Estimated Completion Time. This is the maximum amount of time you have to complete the study. If you exceed this, you will be timed-out.
The time-out feature is designed to give all participants plenty of time to complete a study successfully, whilst timing out those who become inactive.
This mechanism ensures that studies are completed in a reasonable time period.
If you take too long to submit the study you are participating in, you will time out.
Your submission will be displayed as "timed out". Under normal circumstances, you will not be paid for "timed out" submissions.