When I replaced my exhaust, I used new clamps and a drop of lubricant or wd-40 on the worm gear area. They tighten up nicely and I haven't had them come loose at all.

 

Use steel locking wire once you are happy they are tight. You can run the wire through the slot and lock it off, this will prevent them from backing off under vibration. The picture below is for illustration purposes, it depicts bolts with a hole through them but in your case run the wire through the slot and round half the head and twist the wire to commence locking.

 

This would be my suggestion as well.