I realized I don't have a note for Games Done Quick yet, so I'm looking for official information about the event. On the website, the most informative blurb I can find is on their homepage:

Games Done Quick is a series of charity video game marathons. These events feature high-level gameplay by speedrunners raising money for charity. Games Done Quick has teamed up with several charities in its nine-year history, including Doctors Without Borders and the Prevent Cancer Foundation. We are currently the largest fundraising event globally for both charities!

To date, Games Done Quick has raised over 50 million dollars for charity. We also average over 3000 people in attendance at our events, including staff, volunteers, runners, and attendees just looking to have fun and support the event!

However, it doesn't mention how often the event happens. I'm aware from my own experience that there are two "big" events that happen every year called Summer Games Done Quick (SGDQ) and Awesome Games Done Quick (AGDQ). The Wikipedia page concurs, calling GDQ a semiannual video game speedrun charity marathon, but it fails to note a source for this.