Add a global variable and set it's value with get_gametime() on successful touch and check the difference between the current time and that's from the variable.
It should be something like this:
PHP Code:
if((get_gametime() - variable_name) > 360.0) //360 seconds have passed since the last use?
{
//success
//code, code, code...
variable_name = get_gametime() //set the current time for the next check
}
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