I turn my boots inside. They have stiff rubber soles. I can get them all the way inside out except for the toes where the toe split thing is.
I've been doing it for a year or so, and use them almost every day, so invert them that much too. No apparent damage to the boots.
I'm not sure I care if the boots wear out quicker. Wetsuits are a consumable item. It's more important to be warm and comfortable and not stinky than to keep wetsuits forever.
If you don't want to turn them inside out then washing them in a weak vinegar solution works. I used to fill the boots with cold water then splash in a little vinegar. The only problem is it makes me want chips.