I was in a ten hour AV last night. I was able to join it, leave, eat dinner, hang out with friends, and then come back to a still stalemated AV.
We need a three hour timer on AV. Whoever has destroyed the most bunkers/towers at the end wins. If it's a tie give one mark to each side.
I know people are going to talk about Blizzlike and that kind of stuff, but let me make a few points.
The people that join at the beginning of these AV's are not the people who complete these AV's. It's practically a new wash of people every 2-3 hours with the exception of a few.
What happens because of this is...the history of that 9 and a half hour long AV is wiped as the player base switches itself out. This is a problem because the same stalemated situations repeat themselves over and over and nobody has any memory of how to avoid repeating the same situations.
This results in an excruciatingly long AV that holds everyone who want's to do AV on the server hostage.
That's a problem obviously.
If you don't like the idea of a timer....
You should make turn in bonuses easier and easier to get as the hours progress. Wolf riders, and ram riders(or whatever) should be easier to get as the hour marker for AV moves up. EG: Hour three wolf riders should be significantly easier to summon than hour 1 wolf riders. This will create a ramping effect where people can more easily push to end the game, and we can get rid of these 10 hour AV's that nobody stays the whole time in.