Sean Howard 81's page

So I belive I'm the OPs GM. My ruling against multiple instances of the same spell comes from a combination of the rule prohibiting duplicate effects, and the "too good to be true" clause of the rule regarding ambiguous Rules. In this case the effect of sustaining Earth's Bile grants you the ability to drop its AoE. A second casting would override the first casting. You could sustain the first casting and then cast it again to lay down two AoEs in one turn but the first casting would end at that point. The new light spell only strengthens the argument for this since it is an example of the specific overriding the general. Finally I have other players in my game who are not playtesting. So I have to balance their enjoyment of the game against that of what I see as a broken interpretation of the playtest class.