Stick to the checklist - ie if the required drill (as Boeing) says 'wait 30 seconds', do so. Two reasons:
1) Liability issues are protected if it all goes wrong because you 'only followed orders' (as they say)
2) as 'roundwego' says, there is some doubt about the effectiveness of an immediate second shot (ask his partner!!
)
In any case, you always have the option of starting an evacuation during those 30 seconds if you feel uneasy about the wait.
hereford
duty lert