How long can a form be open before it times out?

The form does not time out by default. It means that users can fill up the form as long as they want.

If you want to limit the amount of time your users can fill up the form, then please check these widgets:

Countdown widget
Global Countdown widget

Here's a guide on How-to-Add-a-Widget-to-your-Form.

Hope that helps. If you have any questions, let us know. Thank you.