I have three snakes eating doubles right now:
Inez gets double big pinks, Choco gets double fuzzies, and Zee gets double hoppers. I put both very hot mice in at the same time (container feeding). If there seems to be a longer than acceptable lag between finishing the first and taking interest in the second, I may either move it closer (Zee doesn't always see it) or wiggle it around (guaranteed to make Inez strike) or heat it up (also guaranteed to cause Inez to notice). I probably get impatient and do this one out of ten times, and in reality, if I just left the room for 30 minutes, it probably wouldn't _be_ a problem.
Nanci