It's all about how good or bad the concrete is. The company I work for has over 40 garage facilties. Each with a wash bay, some indoor, some out. All have heated pressure or steam washers. These wash bays have been in use for more than 30 years. None of the concrete sealed. All have smooth surfaces EXCEPT where water leaks have been. Water itself is very abrasive. Dripping in the same place will make the concrete rough. Years of blasting the grease and muck off has not damaged the surface. Blasting the surface is not constantly done although the environment does remain wet for long periods of time. There will be more damage by mechanical means ( dropping heavy objects ) than there will be from the steamer / pressure washers. Concrete quality will vary from town to town, residential to commercial, etc. I can't remember the last time someone checked if the driver watered the batch down or did a slump test for a residential driveway.
But this isn't about concrete, is it. It's about pressure washers. So let's get back on topic and back to the tools.
BTW, for those that mentioned CAT pumps. We have been using those pumps for over 40 years. 3' x 3' units with seperate oilers for our insulator washer trucks. Loud and bullet proof. If CAT's smaller stuff is of the same quality, I don't see how you could go wrong!
