I always have a topwater lure rigged for any species.
For barra i toss it around when ever fishing depths less then 6-7foot. I just cycle through the lures and the topwater gets a run each and everyday if I find myself fishing those depths.
Normally I throw it around for about 30 mins each time I use it and possbily several times a day. Although I do prefer morning and afternoon topwater but will resort to topwater anytime if I feel its worth a shot.
Have not had a heap of impoundment barra experience but what i have experienced and learnt is they will come up to topwaters any time of the day if they feel the need
Cheers
Lee