My experience is in the middle. I generally see AI-AI vassals that are stable for a while, then they declare independence and then they revassalize. I sometimes see it for the entire game but usually not. However, I don't see it every 10 turns either. My experience with MM and Gandhi is identical to yours - annoying predictability.
@ATC1983 - I think it is worst on Earth18. I often see a couple of blocs form and have never seen Mansa stay free.
Sometimes I play with PA on, and then sometimes 2 civs will PA and THEN PEACEVASSAL to Qin. I usually lol when that happens.
Getting rid of vassals. If it's a cap vassal; if you are nearby them, you can sometimes expand your culture so much that they'll actually lose enough land or break away. Warring and not helping works well, sometimes they can die.
For peacevassals, it's very haphazard, but if you keep trading with their worse enemies and refuse to help them, sometimes they won't like you anymore and leave. I find it happening when I cap a few people they hate.
Get rid of vassal states? Heaven forbid!! For those of you who think vassal states mess up the game just because your enemies run in fear from you to hide behind someone stronger, you clearly don't like playing realistically.
Considering a lot of new masters commit suicide by accepting the new vassal, sometimes declaring war on multiple civs (Mind you, the AI usually will never war with more than one at a time, unless the AP is involved, then they have no choice), I don't find the realism argument holding much water. Well, I suppose many leaders were idiotic and suicidal, but hey....
Frequently, they receive NO benefit from accepting the vassal and often get vassalized themselves. They also constantly gift the new vassal techs with no return; their vassals are often more advanced than the masters because of this! Oh, and they sometimes jump to another master and rinse and repeat.
So how does that usually make sense; I thought a master usually exploits its vassal, not throw away its chance to win the game just because it needs to protect some other civ it doesn't even care that much about. Some civs offer themselves at cautious or even annoyed, so it's not like their doing suicide missions for their friends.
It is a good concept, but in game can lead to such annoyances.
Personally I still leave it on because the game is extremely tedious without it, but you can't blame people for having gripes with it.