Thanks for the answer
Actually my example was a little bit obscure

Consider the following cases :

#a departure - acceleration - turn - deceleration - arrival
#b departure - acceleration - cruise - turn - cruise - deceleration - arrival

I think that the permanent shift of time in case b) is higher than in case a) due to the two cruise time intervals at constant speed ( module) , assuming of course that the acceleration , deceleration and turn phases are the same both for a) and b)

b) is a pratical case of a shuttle which remains in the space for a long period
I mentioned in my previous post that a starcraft travel at about v = 40.000 km/hour
Suppose it remains in the space for 1 year
If you put these data in the simple equation of the special relativity for the time dilation, you get a time shift t = 3 - 4 secs

Well this is exactly what has been experienced in the spatial missions
The clock on board were found 3-4 sec late on the arrival

Summing up

I did not mean that all the discussion about the change of " inertial frame " etc are wrong , I mean they are redundant

The "essence" of the twin paradocx lies the time / space symmetry
whereas the twin at rest "moves" only in time , the pilot "moves" both in "time" and in "space"
The time shift is a immediate consequence of the fact that time and space are related items , even though it is hard for everybody to really grasp this claim
For common sense time and space are unrelated measures