Got a 256GB XS Max here.
I feel 512GB is brilliant and in my next iPhone I will get a 512GB OR 1TB variant.
Currently with my 256GB, I have used 60GB, I set my Video Recording to 4K@30FPS, I download all my Playlists from Apple Music and Tidal, also like having a few Netflix episodes of my favorite shows and YouTube videos of my favorite content creators downloaded for when traveling, so it helps to have a lot of memory. I have only had my XS Max for about 2.5months, I fully expect to continue filling its memory up.
My music library in particular is forever growing so one day I will need to jump to 512GB.
I cannot wait until there is a Max 1TB variant, THAT would be the sweet spot. I like having my media offline as I am not always near WiFi and 4G coverage can be spotty.