With my kind of person and activities level, that 64GB would get full in a matter of just one month.It all boils down to individual preference and the nature of work. I don't download much therefore 64GB is enough for me. As technology is advancing, soon we may have 500GB in smartphones.
I do store my important files in my email and Evernote. I think is farcmore better for security purpose and to make sure my phone is free from storage related problems.With my kind of person and activities level, that 64GB would get full in a matter of just one month.