As i understand it on newer systems, some % of the memory space are set aside for event files, and these will also get overwritten as that memory space fill up.
But how large % of the total memory space i dont know, i did a little testing with my SG9663DC system and it was not a small amount, but the exact number i can not recall, just that with just a little due diligence you dont have to be afraid your event will be lost in recycling.
Older systems like Lukas, you could choose how much of the memory card you wanted to set aside for events, but that is not the case with many or at least some of the newer systems.
Thinkware and Blackvue ASO i still think they let you decide event space, but not sure if those then recycle footage within that space