I've had my Karcher for heck ----- erm ----- 10 years now. Still going strong!! I've only had to purchase a replacement lance about a year ago, apart from that it's been solid.
They say you shouldn't store them outside, due to the frost etc. I've had my unit outside for the last 4 years and it's not bothered it in the slightest. Very robust, works as it should and would for sure by a Karcher again. Oh to note, it is also used pretty much every weekend!
The test on the gadget show was fairly pointless, as mentioned the industry standard squirt the elephant dung across the floor is really no measure for pressure power. If I put my Karcher on the stream jet it would have flung it back up the elephents @rse! So that test was pointless as the Karcher failed, clearly because he had it on the wrong setting. Which would proabably apply to all of the units for each test.
It seems John was given the task of testing jet washers.... he clearly didn't know how to go about it and thought turning into a light hearted test would keep the viewers interested.