On any given day with a session manager I would have over 400 tabs "open at once". The thing to keep in mind is that when you restore a session in FireFox: the tabs that are actually loaded are not greyed out.... the rest are kinda just there... I'll scroll left and right in my tabs for what I feel like doing: Left for when I'm alone and right when I'm redditing and shit.... and a bunch of tabs in the middle for actual work... its a great way to hide porn actually, nobody wants to scan that many tabs for what they think I might be doing.
Did your dad ever learn that was wrong?