Engaging them without support is inefficient. It becomes a troubling drain on resources limited without an active Master on hand.

...Are you not concerned, Emiya? A pair of Servants with an absent master are liable to become targets before long, should there be worse out there than mere walking snowbanks. Even I can't create an engine to generate perpetual magical energy.

[The brief look on his face seemed to say '...or could I', completely unaware that the other Archer might find his name being used a little suspicious.]