Hello!
You might consider the differences in distance. From the UFO Yards to the base where you are dismantling the UFO. The longer (or farther) the distance between UFO Yard and the Base with tecs, the more time its going to take.
So from the same Yard, if two bases with same amount of tecs are unequal in distance, the farther base will take more time.
Not sure if this is what you meant though.