Ask HN: Should I convert all H.264 into H.265 for disk space?

Some of my phones do not record H.265. Those do record H.265 like Xiaomi or so provide an option to share as H.264 for compatiblility.

But the advantage of H.265 in terms of disk space is massive so I want that.

But I am afraid of availablilty and performance that made me unable to play those on some computers or future phones and tablets.

What's your idea?