I was going to put mine on a treadmill to get a few miles. Works with dogs and people, should work with mistresses as well.
I'm all seriousness, when I am spending $13,000 on a brand new sled I can have a little self control for two tanks of gas. I guess we may know who not to buy used 850's from.
You? I mean you no offense, but only seek to educate some. You should exercise control in not holding steady throttle, but that's about the only rule. You want to load the engine; both acceleration & deceleration (down shift a car, let off throttle on a sled)
Many may not understand what happens if the rings don't seat properly. There will be more combustion gases leaking past the rings. For one that's less force going into turning the crank, but also proper heat transfer from the piston through the rings to the water cooled cylinder wall doesn't occur as efficiently. You do an engine no favors by babying it during the short time that the ridges of the freshly honed cylinder wall are present to wear the ring down to "fit" and seal to the cylinder. Once they're gone, the engine won't break in any further whether things are seated or not. It's even more of an issue in a 4 stroke with lubrication oil being contaminated with the blow by.
Machining is quite good these days. You're not "wearing in" the bearings or anything like that. If the bearings lock up during break in, they were defective or there was a serious oil issue. If the engine is warmed up and assembled properly, there's nothing to worry about.
I know it feels weird to ride something so new hard. My 800 was treated that way the day after I picked it up. I pulled the head a few weeks ago and things look good internally. 3400 miles and compression is dead even. I just went through this with my pickup too. Built the V8 & installed it, warmed it up & set timing, quick check for leaks, then take off and step into it. I sent in a used oil sample for analysis after a few hundred miles and the text in the report said "good job on your first V8 build, your engine is off to a healthy start". I mention this because the truck was driven hard initially, but there is nothing indicating excessive bearing wear or other damage. A while back, I built a Polaris 800 a few different times. Once was gentle break in and another was hard break in. Gentle break in left black deposits below the rings from excessive blow by. Hard break in and the pistons were clean below the rings.
I didn't come up with this stuff, this guy did:
http://mototuneusa.com/break_in_secrets.htm
I'm not implying you'll have any real issues if you baby your sled out of the box but it won't help you in any way.