FASA Games, Inc.

When a damaging spell such as Ephemeral Bolt has a duration, does this mean the effect test can be reproduced each of two rounds? Or is this a "you don't have to blast the guy this round if you don't want to; you can wait until next round" kinda thing?

In most cases, the damage only happens the first round, it is any secondary effects that last for longer. The descriptive text of the spell should indicate what effect(s) of the spell last beyond the initial casting.

In your example, the damage is done if the spell hits, and then the -2 penalty to Willpower tests lasts the duration.