I don't think they could ever explain their labyrinthine rules and exceptions and clauses on their own message board, so I doubt you'll get a clear answer here.
Can't speak for now because I haven't promoted them for over 5 years, but back then IIRC they had a 14 day cookie or some such bullshit which, AFAIK, meant revshare ended after 14 days.
Personally I found that absurd, but I guess it works both ways, since it means other people can't lock in a referral for life, so you can make money from someone who has already been referred.
As for this cookie thing, ironically I think it may have come about by request of affiliates. I seem to remember years ago people complaining that their cookies were being overwritten by cookie stuffers, so AWE made it so the cookie couldn't be overwritten. I could be misremembering that though.
With a cookie with a very short life it makes sense and seems fair to me though, because if you refer someone to a site and they don't sign up immediately, but come back to it a week later, if they've been to a site that has stuffed a cookie in the meantime then you won't get credit, even though you're the one who originally referred them.
Basically people will complain whatever system it is, if it's not their cookie that's counted.