Question:
Answer:
We should not leave the Mass until the dismissal. Ideally we should not leave until the closing recessional (permitting the crucifix of Christ to lead us into the world).
However, there could be very serious reasons to leave earlier. For example, if someone has to return somewhere to care for a child, an elderly person, or a sick person. If someone has received an emergency message. If someone needs to get to work and the Mass has run longer than usual.
Outside of having a serious reason we should remain until the dismissal. We should attend Mass not simply as a “me and God” experience but as a member of a community, as a part of something larger than myself. Leaving early without a serious reason focuses our attention on our own personal desires rather than committing ourselves to the Mass and our brothers and sisters in Christ.