In order to get timely feedback from stakeholders we have built a fixed duration into Vvs of five days. As soon as a Vv is published, an email invite is sent out to all specified invitees. In that email they are informed that the Vv has started and when it will expire. When people browse a list of Vv in the Visual Vocal mobile VR application, they will also be informed of how much time remains in the feedback period for the Vv.
After a Vv expires, people with appropriate permissions can still view the Vv content -- they just will not be able to submit feedback.