I played the MMRPGs mostly as play by post, so it is difficult to say about them, but the couple of episodes that were played face by face ended on time, although the GM did actually manage the times according to the expectation of ending them in a single session (occasionally pushing the things a bit to end on time...)

Now that I run more episodes, I can say that some of them would be really difficult to be completed on the scheduled time (for example The Redwood Scar, that by the way is one of the best adventures).
In general, it looks to me that on the first season it was easier to find episodes that can be easily run in half a day (exceptions were few), while later on there were more opportunities to drift.

Interesting. I never paid much attention to the time aspect of the MMRPG. How important would you say this is?

Well... it depends on how much time you have! :lol:
If I play a face to face game recently I want it a one-off, because I know it won't be easy playing the follow up anytime soon, so for me it is important being able to complete everything during one evening (so the standard 4 hours timespan is OK for me) and not being able to close is a disappointment (typically forcing the GM to cut pieces of the adventure to achieve the end of the story on time).
I believe that playing a game in an almost competitive environment at a convention (I understand that this was the original duty served by MMRPG adventures) requires as well being able to close on a limited time or being disappointed (and on this occasion the GM probably won't feel like cutting down the written adventure to facilitate the players, as there is that competitive edge), so I guess that on the first adventures the authors were very focussed on time and perhaps later on this aspect was a bit less of a focus.
What do you think?