Many interesting ideas in this thread, but most of them don't consider an "overall view" [I hope my translation be correct] to the many features already existing on VDip.
I agree with the first part of fasces' last post: in my experience, most of NMRs are from:
1) Beginning of the game. It's mostly by Newcomers who joined a game and then leave the site or don't feel the importance of commitment yet. This issue is already solved by the "NMR Policy" option, that let you have the time to find a replacement without letting the NMR screw the game. If you create or join games without this option enabled it's your fault, so don't complain about NMRs screwing your game.
2) Later in the game. It's mostly by "sore losers, who stop checking the games they are losing". There's nothing you can do about it. No new feature will make these people willing to check their games more than RR-system already do. If they NMR anyway, then they deserve a bad RR.
What I don't agree with fasces is "It seems that around 50 days into a game, people start getting bored of the game and will start forgetting to send orders more and more."
Personally, I'm interested in any game I'm in alive & fighting. No matter whether it started yesterday or 6 months ago. To me, it's a mystery how someone could, at one point, lose interest in a game.
Anyway, whatever the reason be, I believe that people having problems with games lasting more than, say, 50 days should just pay attention to what game they are joining. There are already several features on this site helping these people:
a) http://www.vdiplomacy.com/variants.php The 4th column tells you the average duration of a game in that Variant. So if you're going to join a karibik (20.88 turns) with 1day/phase, it will last AVERAGELY 50 days. Probably more, so, if you have this interest-decreasing problem, don't join it!
b) another VDip's feature, helping you and making things even simpler, is when you join a game a box appears and asks you:
>>The game will start when all 12 players have joined.
>>Looking at our stats this game might take (roughly) 5 months, 8 days to complete.
>>Are you sure you want to join this game?
so if your interest-decreasing problem makes you hate games lasting more than 50 days, WHY THE HELL DO YOU CLICK "OK" ?!?!?!
c) EoG feature. If you want to play a (usually) long Variant but you don't want the game be too long, you can enable the "Alternate winning conditions/Max.turns" feature when you create the game. This way you'll know your game won't last too long.
I believe that people who know they'll lose interest in a game after a couple of months, but pay no attention to the games they're going to join, are not much different from people who lose interest when they're losing the game. They all have a problem, but it's not our problem until they can NMR and have the bad RR they deserve.
So, I totally agree & quote Podolski:
"you go for fast games if you want, but the correct MENTALITY is that once you join a slow game you should stay committed."
This site got already many fantastic features provided by Oli. Just learn to properly use them.
After Newcomers and "sore losers / interest-decreasing", the third issue is that there are NMRs on weekend?
Well, we already got a feature. Most of extend-requests I see in my games are on Fridays. They're usually from committed people who care about not-NMRing. But most of other players don't vote for them. You've got to conclude that MOST OF PLAYERS DON'T CARE ABOUT NMRs.
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This was my "overall view".
IMHO, we already have enough features to handle all these issues. What we don't have, is enough people caring. It's a mentality issue, you can't solve it with a new feature.