I break my engines in like I plan to ride'em. The Banshee ... I let it warm up & then it's "Balls-To-The Wall" ... never had an issue & it runs great. It also has lasted a long time.
Now I just did a big bore kit in my 660 Grizz ... I'm break'in it in the same way, like I ride it. I let it warm up, then it's slow for a bit & then WFO for a bit. Pull hills fast & hard (depending on the hill of course) ... crawl over rocks & logs, and then WFO again for a bit. I don't baby it one bit.
And here's my reasoning ... I had a Honda 185 I broke in the way you're suppose to ... slow & easy. I had a friend who also had one & broke his in "The way he planned to ride it ... WFO !!" ... The SOB always kicked my rear-end. Or I should say his bike would beat mine. Cause when we switched bikes, his bike (with me on it) would still beat my bike .... the bast%$# !!!
So, bottomline ... I'd break it in the way you plan to ride it. If you do a lot of slow rid'in, I'd definetly throw some WOT runs in there to "Work" the engine a little .... anyway, that's MHO ... but what do I know ?? ... besides, whichever way ya break yer motor in ... enjoy the crap out of it coacho !!! ... WOO HOO !!!