If the business is very busy, and you are doing a good job, they may ask you to stay a bit longer to help. If you are available, and would like to stay to help - by all means, do! But don’t feel you have to, if you cannot for whatever reason just let them know.
Just as a reminder, overtime payments are processed separately to the overall Stint payment (we are working on this and aim to have it changed ASAP!). In order to receive payment for your overtime, please email firstname.lastname@example.org with the date, name of the business, amount of overtime and the originally scheduled hours of the Stint. You need to apply for overtime within 24 hours of completing the Stint as all overtime claims will be cross checked with the relevant businesses.