What I normally do is the following:

action dummy()
{
...
my.skill1 = 5*16; // 5 seconds
while(my.skill1 > 0)
{
...
my.skill1 -= time_step;
wait(1);
}
effect...
ptr_remove(me);
}

Then you can easily use events (for impact detection and the like) where you set skill1 to 0.