+1 I wish I had left mine on. Same reason. Replace them when you get sliders, or after they get damaged, unless you really can't stand the way they look. They will offer a modicum of protection from rocks. Not much, but some. When they get banged up, you shrug and pull them off anyway. In the meantime they really do make it easier for kids and shorter people to get in.I'd keep the running boards on as an "early warning" crunch alert. Matter of fact, if using for anything other than rock crawling/extreme overlanding, i would keep due to a) weight b) cost of sliders.
Ask me how I know...doh!