If you have an Express cruiser with one/twin bravo 3. I'd worry more about changing the oil annually than drive showers. And don't forget to remove the reservoirs and flush the sludge out of those. Now if you're going WOT as soon as you leave the boat ramp. Sustaining it all day long, which I don't believe you're doing with an Express cruiser, then a drive shower may help you. MAY... If you had a go fast boat sustaining high RPMs. Then I would spend the money on drive showers. If you have a go fast boat and are only doing 40 mph. In my opinion. You don't need them.

IF you read some of @t500hps posts, he was shopping for a 400SS for a while. He settled on a Volvo diesel/drive setup.

Why? Paraphrasing: Every single 400SS with Mercruiser gas engines and B3 drives just had "new drives" installed.
There's a pattern there worth paying attention to.

Anything you can do to make things better on the drive is meaningful.
One of the reasons why I like the Max Machine Worx setup (I think that's what F2s-speedy has along with an ungraded/stronger top cap with the cooling dumps within it)...
...is you can pull the drives and switch them side to side to wear the other half of the gear set. Then just swap the drive shower pick up to the other side.

There is a dozen things that can happen to a bravo 3, or any drive not heat related. For instance when I had a Sea Ray Sundancer with bravo 3's (purchase new and had it for 10 years) the only thing that went bad on them were the inner propeller shaft. Heat treat problems. The oil seal wore into the shaft creating an oil leak. Mercruiser fought me on the warranty, but finally paid the whole tab. Would cruise around in that doing 35 to 40 mph. Never had drive showers. Never showed signs of getting hot.

Not a Bravo III but with my XR I get a white chalky deposit on my drive ....with a shower, I don't.

Padraig