Your right about that. I usually don't keep cars for more then 3 years as well.yeah makes sense.
for me dash cam are just cheap replaceable items and it makes no sense for me to keep it and move between vehicles. I am OCD and I tuck all the wires, and I run front AND rear cams so it really doesn't make sense for me to undo all that just to move to a different car. Besides, chinese electronics are not made to last anyways especially when exposed to the extreme heat in the summer and extreme cold in the winter. also dash cam technology do get updated with newer higher resolution etc.
2-3 year would be a good time to upgrade/ renew. they're cheap enough anyways a few hundred bucks.