"This seems to be highly sensitive to the amount..."

This seems to be highly sensitive to the amount of time EAs currently spend on deciding. I think that most people are likely to end up not donating at all if they feel pressure to spend more than 2 hours making a decision - I'm not sure if EAs are selected enough to mitigate that factor.

I also moderately believe that most EAs will not use the extra time very well (e.g. just pouring the extra time into more detailed analyses of two similar causes).