Welcome to our forum.
I can understand switching to Bromine only if you or someone in the family has a strong sensitivity to Chlorine, but just to switch because you may only use the spa once a week is not necessary. I use my spa maybe 1 to 2x every two weeks and use Di-chlor and CD Ozone as my treatment method. If I use it, couple teaspoons of di-chlor when I get out. 1x per week, 2 tablespoons of di-chlor as a shock, and adjust ph levels 1x per week if necessary. Water is sparkling all the time. May take as Drewstar said 30 seconds out of my day.
I bet you could shock less often too.