Don't mean to sound condesceding but it probably will however I write it. So apologies in advance…
Do you know how to punch properly? You can really 'goose' your wrists by punching a heavy bag incorrectly.
As for workouts just vary the speed, strength and punch type throughout the rounds. I'd start with 1'30" rounds X5 to start with and then increase the length/number of the rounds as your fitness levels increase.
Bag work is very good exercise and if you push yourself hard enough even the small amount of workout time that 1'30" sounds will be enough.
Hope it helps a little