Actually the dependability is not in just showing up but adding something well thought out to the game. While a Dungeon Master / GM could be there for you when you need him what will be the point if there isn't any backbone to the game itself. A lot needs to happen in planning long before a Dungeon Master / GM attends to your game and that is part of the dependability factor, or at least it is for me.
If you don't enjoy what you are doing, then stop doing it.
Role-playing is a mix of give and take on both players and game masters parts. There really is no balance saying "This much is required," as game needs dictate not a prescribed set of rules.
Then the question has to be asked why would someone want to take on being in charge of a game if they do not enjoy doing it? Were they just testing the waters or saw their own weaknesses come out when the game started? Even if they do not enjoy it I feel once they start they should at least gracefully wind it down rather than just leave. I've read the complaints of players in the past who did not like that they did not even show the courtesy of saying they could not do it anymore.
I hope to pay more attention to our Dungeon Masters / Game Masters / Referees here for 2016. I want to render support and assistance so they can bring about the most exhilarating, and consistent Role-playing Games possible. One possibility, which might be rare, is a GM assistant. Someone who can continue the game when the GM cannot be there. That should bring some definite dependability.
Dependable Dungeon Masters can be harder to come by, especially those willing and able to stick with the game for the full campaign. I myself have had games that lose momentum either because players not sticking with the game or I admit because I wasn't able to commit like I had hoped.
It can also be stressful, even when things are going well, which is why finding a group where the GM and players work together to encourage each other is important. If not everyone is having fun and enjoying themselves it can drag down the game. A dependable GM will to keep moving forward even when, ore especially when, the going gets tough is something to hold onto and encourage.
Edited: Thomaslee on 9th Jan, 2016 - 1:58am
One of the big things online that many feel they do not need to be is courteous. I can usually tell when something will not last long but I tend to give it the benefit of the doubt, sometimes to its demise. Another Role-playing Game abruptly closed and we only found that it was abandoned because after a week I inquired about it: Read More.
Other Game Masters in the past have had real life issues come up but at least they have returned to say 'x' happened, I won't be around for 'y', etc. This is the courteous thing to do. Do not be short sighted in believing that you are the only one with real life issues because you will be living an illusion. You started something - finish it. If you can't at least be courteous enough to let us know, ahead of time even better - or even the best: do not start Role-playing Games that you can't finish.
The GM lieutenant sounds more interesting in these situations - someone that can take over as GM.