I have no idea about the FE 550 per say, but I've been riding the KTM's for quite a while now and I can speak with assurance about the 525. I suspect, with the new materials used in these bikes, the Husaberg included, the service rebuilds are actually a lot farther apart than the manuals call for. As evidence, I'll present the case of my 2005 KTM 525.
I purchased it new, I immediately converted it to a dual sport by adding lights and getting it licensed for street use. I then rode it, maintained, rode it, maintained it, rode it, maintained it, you get the picture. As it sits in my garage right now, it has 35,000 miles on the engine and has never been apart for a rebuild. It uses zero oil, and I took it for a ride yesterday to circulate the fluids a little, and it still runs great. Did I have any problems during those miles? Yes, I replaced one rocker arm that lost it's center bushing on the roller end, and I lost two bolt heads on the cam retainer caps. Otherwise, a lot of rear wheel beearings until I went to the oversize bearings ofered by MSR.
I actually had fewer problems with the KTM than I had with a previous Honda XR, a bike which are considered bullet proof by almost any standard. The XR lost an exhaust valve seat and had to have stainless valves and new seats, and it also lost two clutches in 20,000 miles.
So, now I bought a new Husaberg FE 570 S. It is built by the same folks who built my KTM. Right now, I've put almost 4000 miles on that bike. I love it. Here is what I do to keep them running. i ride a lot of off road, so after every ride, I maintenance the bike. It gets washed, the filter gets cleaned, and it gets a through check over. Any little biit out of order gets repaired. Then during the week, I ride it back and forth to work every day. I change the oil and filters every 1000-1200 miles (yep, that's a lot further than is reccomended by the service manual) with Motorex full synthetic as reccomended by the factory. I check sites like this and see what the little issues are that people are complaining about, then I usually fix those issues before they become a problem. I find it's easier to fix things before they leave you stranded. There is no other big secret here. Buy what you like, maintain it well, and ride it like you've stolen it :cheers: