I'm not upset.
I don't get the question though. The duration of the journey for B is very long and acceleration at the beginning and deceleration at the end should be neglected. That's ok, we could assume (*) that B doesn't have to accelerate/decelerate at all, for example he has already some speed, flies by the earth and in that moment synchronizes clocks and compares them at the end of his journey. (Just to avoid that we're again talking about different things - is this what you mean?)

What I don't get though is what you mean with constant speed. Do you mean the modulus should be constant? Or how is turning around managed for B? Since, when the direction of his travel changes, he also changes his inertial system and his internal clock (or better: the relation internal clock - exterior clock) changes in a non-trivial way.
Having said that, if you would calculate it like that anyway - wrong, though - and just take the time to be the same for B before and after he has turned around (neglecting the time which passed in between) (assume for example that B flies away from earth and then, instantaneously, has turned around and now flies back to earth, neglecting all physical effects this action comes with) and plug in special relativity, you would get a paradox. Namely, for B, A has aged slower. At the same time, in the rest frame of A, B has aged slower. According to special relativity, both are correct. When they come to compare their clocks, clock A shows less than clock B in the B fame and vice versa. Since both clocks are at the same place (on earth) when they compare them this result is nonsense.
=> something has to happen during turning back.

Note the "=>", since this is actually a valid proof - we can describe physics during flight with special relativity and we haven't cheated at the beginning or at the end when we assume the experiment conditions to be as stated at the beginning (*). You can check it, or ask Error if you trust him more.

So I can't answer your question. Could you restate it?

So let me ask you a question: How - with which formulas, which theory - would you describe the change of flight direction from "away from earth" to "towards earth", so that the outcome of the experiment unambiguously gives the result "B is younger than A"?