Sheep the Diamond
Ok, let's see
With my former main Gowron (153d4h2m) and my current main Mardah (55d8h6m), AD clocks in at a grand total of 268 days 23 hours and 10 minutes (probably more by the time anyone reads this).
One of the send-away realms, Lamars the rogue is there with almost 12 days, and it's clocking in at around 12 days.
Another send-away realm. Cymar the lock (8 days) and my undead hunter Vornik (1 day 19 hours) are staioned there, clocking in at around 11 days.
My former main realm. Most of it is gone, but still around 15 days.
And then there are the realms where I only have 1 character, or there are the chars I have disbanded (most notably a 72-paladin and a 40-mage). And the fact that I also had access to another account sometimes. Let's estimate that on around 15 days, seems reasonable with the levels gained.
So, that would made it around...mmmm...310 days I played world of Warcraft..... that's about 10.5 months.