2-3 months is a stretch. I mentioned before each 5 minute 4k video is 850Mb. I drove my car 7 hours yesterday, more than filling up a 64gb card. You don't NEED a 256gb sd, but for less than $20 I recommend getting one.Why? You planning on saving your videos from last year? Lol
64GB is plenty. If you drive it daily it gets you about 2-3 months before it overwrites old content. If something happens and need the video, you are going to download it immediately. Not wait 3 months.
Plus, you can pull the card and save anything to your computer if your worried about losing it.