Believe or not, that Brawler carb was straight out of the box too. We barely touched it aside from the idle mix screws. I live about 2000ft higher than where the dyno is so I ended up jetting it down 2 steps to lean it out a bit. Aside from that, she was the star of the show. Love that carb.
Rebuilds really depend on how badly I abuse the motor and how many bottles I go through. My machine shop is excellent and uses the correct torque plates. I also check my oil and plugs religiously, so until the motor starts telling me there's a problem, there is no set mileage. I'm only using a 150 jet. In theory, it should live a very long time at that level. But if I start seeing a lot of metallic in the oil or I suddenly get detonation, then it may be time to dig into it. Just depends. The motor is constantly talking to you.