I think for these types of children (personality clashes etc) the time also makes it harder. I've had my little one for 2yrs this January and there are things that just drive me up the wall...and I think 2yrs of those personality quirks leaves a little less patience on my part. I find myself having silent mental talks all day. "She isn't trying to be annoying, she is only three, she doesn't know any better" on and on so i stay sane. But by the end of the day at the end of the week I admit I sometimes count the days till she moves on. Then I remind myself that the next kid will likely be a terror and I'll regret ever thinking it!

I suppose at the end of the day I would much rather have to put up with the annoying personality quirks of a fairly well behaved child then to start new with a child that is out of control and needs constant shadowing.