Detection for each skrimish?

By Destrucity, in StarCraft

3 dark templer vs 3 whatever . Do I really need a science vessal for all three skrimished, or is one enough for the whole battle? My group has been playing that one is enough, but when I rereading the rules it mentioned only in the skrimish. What do you guys do? Is one enough?

Assist units provide Detector for single skirmish only. Only technologies (Scanner Sweep, Observers) and Air Support module work in all skirmishes.

one more soluation as usually to do is Splash them.