Used 2 box, how I started, had quite a few alts before then, and then had more ideas of what I "could" do if I had more accounts, especially for instances if your mount farming, its handy to have a few accounts as your not going to have to share that /roll on a really rare mount drop.

Awesome for boxing professions, especially JC x5 lol and DE
Alchemy when truegold was profitable etc

But yeh, now I have 7 accounts... tho I am possibly closing 1-2 off, and keeping the solid 5.

never ever could I go back and play 1 account.

Only time i am really actually using 1 account is when I am raiding on my main, with my guild... and thats just a few hours, few times per week.

Its just to damn good, to have multi-accounts and do things without idiots in the way, or being disruptive etc