The issue is, every time we make a great leap in storage medium, we tend to use that new storage for BIGGER files. Higher quality media and all that. Back in the day, the average movie file was measured in the MB. Now it's GB. Think about an old floppy with 1.4 MB of data and how many text files you stored on it. You couldn't ever imagine needing more space. Then came pictures and music files. Video files. Then higher resolution picture and video files. Suddenly even your text documents aren't just raw .txt files, but Word documents and interactive PDFs.

As storage improves, what we expect to be able to carry around with us or have in our home computer changes. I'm currently running a home server with 18TB of storage. An amount that I would have never dreamed of possessing 20 years ago, and yet here I am debating when I grab that 24TB drive because I can already see me running out of space in a few months.

This is all to say that I really don't think there will ever be a maximum amount a user could need. Give them that maximum and in a week they'll have figured out a way to use it to capacity. I think video games and cartridge/disk size limitations and then the transition to digital games and balloning game size shows my point.