My Craftsman PW is 7 years old and still runs great. However it's the pump that may cause the most issues. I always, without fail, flush the pump with "pump saver lubricant" after every use. WITHOUT FAIL! Never a problem doing that.
I have a Karcher that is about 9 years old and 2 years ago it wouldn't spray very well so I had it taken to the repair shop. All that was wrong was a stuck valve in the pump and it works like new again. The repair man told me to run anti freeze through it before storage so I grabbed a gallon of anti freeze and poured it in the inlet hose hole and started it up/shut off/ repeat. I did that a few times and I know there is anti freeze in the pump and keep it in my heated garage. It should be fine this spring. This unit has a Honda engine and was told it has a plastic camshaft however they run quite a long time according the the repair man. I am very happy with the unit for only around $350.00 and I would consider them a throw away if the engine would blow. It is not a clone engine either it is a real Honda.
From what I've seen the plastic cam and carb hold up ok, but I'm not a small engine pro. FWIW I have an old B&S cheap Bolens push mower that was made in 2007 according to the engine number and it still runs excellent after I replaced the gasket and diaphragm in the carb. It seems like the engine will outlast the deck. My neighbor was going to throw it away because it wouldn't start.