You could use mIRC's built in flood protection which will queue your own messages to prevent flooding, or add to the script a routine to prevent flooding. To do the latter would be something like on the triggering add a number to a variable that is set to expire after a given time. Also, the trigger will check to see if the variable has already exceeded a determined value.

example:

alias noflood {
if (%flood > 4) { return $true }
if (!%flood) { set -u15 %flood 1 }
else { inc %flood }
}

on *:text:*:#:{
if (!$noflood) {
[rest of the trigger code here]
}
}

The benefit of using a single alias instead of adding similar code to a number of triggers is that it will prevent several different auto-response commands from a bot or such being able to be exploited to flood it off. That said, it is still probably preferable to use mIRC's built in function for this, as the responses will still occur, they will merely be offset in time to prevent flooding.