Soldato
Don't think it's that unreasonable. Just looking at my Xbox One's usage this month (the one in the front room) and it's at 500GB, from streaming Netflix, Amazon and Sky, and downloading games.
My PC is at 450GB from a few new games I bought, updates and some hefty applications for work
My laptop is at 200GB, mostly from Adobe's suite, FCP, Motion and all associated plugins
Edit: Just noticed TV has done 300GB too
In a busy household I think it would be easy to hit 5TB across multiple devices
Edit 2: Im on 150Mb
My PC is at 450GB from a few new games I bought, updates and some hefty applications for work
My laptop is at 200GB, mostly from Adobe's suite, FCP, Motion and all associated plugins
Edit: Just noticed TV has done 300GB too
In a busy household I think it would be easy to hit 5TB across multiple devices
Edit 2: Im on 150Mb