|Just the opposite. This would create a great deal of unnecessary work for you.|
As well as being the permanent thing that resides at your group's web address (prestogem.com/vo/xxx), a group contains a database: everyone who has registered, your draft messages, your report definitions, and so on. In other words, creating a new group for each event would mean re-entering all this data each time you had an event.
Additionally because this database also contains all your events, schedules, and signups, you get the benefit of having a group history. You can quickly create a new event with the same sort of schedule as an earlier event (using Copy on the Create Event page). You can display the past work experience that people have (using reports or Search for People).
Note that a PRESTO event can be used for essentially any real world thing you want signups for. It might be a meeting, a fundraiser, court reservations, worker shifts, a survey, and so on. It might be short as a day (as for a meeting) or roll on forever (as for court reservations). For more info on PRESTO terminology, see the Feature Basics link on Admin Home.