[Wierus]

I would be doing oil changes every 10 hours (minimum) as well, or after every trackday.
My main bearings failed just shy of the 200 hour mark, possibly due to shitty oil. It had a lot of race hours on high speed circuits though.

 

[Wierus]

I think the manual recommendation is really conservative, but my stock piston had a little more life left in it after 160 hours!

 

[Wierus]

well a lot of the engine components are the same as the EXC

 

[Wierus]

Does your 690 stay with 600cc sportbikes up to about 80 MPH? Doubtful. Has your Husaberg's computer had it's fueling remapped? My 570 has the dealer-installed "akrapovic race map". With a slip-on muffler, air filter, and remap the bike puts out quite a bit more than stock. Plus my 570 is 60 pounds lighter than a stock 690. If you are not riding the 690 like a supermoto and instead are riding it like a tourer, then it's the better bike for that purpose. If you actually ride "supermoto-like" then there's no question the 570 is tops. I say "supermoto-like" because some folks only ride on the street but in an aggressive manner (when/where appropriate). I run a 45 tooth rear and 15 tooth countershaft (3.0:1 ratio) when I want to travel or otherwise put down miles. The bike rips with this gearing. Change the countershaft to a 14 tooth (3.21:1 ratio) and it accelerates even harder. I get an easy 110 mph with the 3.0:1 gearing. The stock KTM 450 SMR run 14 and 48 tooth chain wheels for a 3.43:1 ratio. I have yet to try it but will put on a 13 tooth to get to 3.46:1 ratio. I think 1st gear won't be of much use though.

A slip on and air filter adds fuck all to the peak horse power on the 570. I've done before and after dyno runs. It does increase torque and shifts the curve to hit sooner in the rev range.
The Husaberg's primary fault in terms of outright power is the air box. This becomes clear when you cut a hole in the seat. Dyno runs with the seat OFF gave around 3hp at peak. You need to do a lot of engine work to get the 570 to have the same kind of punch as MX based 450's.

Trust me, I've been down that road. My empty bank account is proof

Once you do spend the coin though.... Holy fuckballs.