Specifically I am curious how many hours you put into individual games as well.

I get that MMOs can have nearly unlimited replay value in some cases. But i am wondering what numbers MMO vets push in these kinds of games.

Depends on the game...Ultima Online I subscribed to for just over 7 years, Dark Age of Camelot I sub'ed to for 5 years...if the MMO is good it can be very difficult to put down...In UO where there were dynamic fiction events put on by in game dungeon masters (Seer's) and these storylines could take the server a year of real time to complete. It was not a case of IF you would login each day, you HAD to login because your character was involved in this amazing dynamic storyline that if you did something that changed the story you could make it go in a new direction by your actions, and you had to be there every day for that to happen and not miss out on the opportunity when it came your way...I can remember rushing home from work and eating dinner while logged in every single day because I had to be there simple as that...

RS I put 10 years into, WoW a good year and a half, Lotro 2 years. I'm not by any means a "veteran" in the standard MMOs. There also hasn't been a MMO good enough for me to spend 15/ a month for large amounts of time. Runescape was the only one I invested significant amounts of time and couldn't leave because of that simple fact, and it's certainly not close to 15$/month - glad I broke away from that game, it just wasn't worth it anymore. Lotro I pretty much can get to max level on all my alts without having to pay a dime because of the money I had already invested, but the combat is lacking far too much for me to continue anymore.

In WoW I had just shy of 600 days /played on my main when I quit at the beginning of Cata. Total account wise was just shy of 1000. So far I am at just over 400 hours in Skyrim, but then I have also spent more time actively modding it (checking mods etc) then playing it.