Here's my experiences so far-
1.- I ran a MS-460 Big Bore kit from Bailey's from spring of 2006 to spring of 2007 on a rebuilt MS-460 while I was cutting timber as a contractor for a logging company out of Glide, OR. The last sale I cut with that saw was 4.25 million board feet of mostly straight falling (sending trees straight down the hill, to be yarded out tree length and processed on the landing.) It had OEM wrist pin and clips, and OEM 066 rings. I was cutting mostly softwood (Doug Fir, Incense Cedar, some Ponderosa Pine, and a little Chinkapin.) That saw ran great and the cylinder had minor port work done by me. After the last sale I traded it to a fire wood cutter for a load of wood for my grandmother. I had approx. 600 hours on that top end. That saw cut firewood for two more years before the bottom end went out.
2.- I ran a MS-440 Big Bore kit also from Bailey's, also with OEM wrist pin, clips, and Caber rings on a snag falling job for the U.S. Forest Service at Diamond Lake, OR., in 2008. I cut approx. 700 snags, mostly Lodgepole and Shasta Fir, varying from 13" to 60" in diameter. I had about 300 hours on that saw before selling it to a member here. Last time I checked, it was still running good as an occasional use firewood saw. It also had mild port work by me.
3.- In the winter of 2009, I built a Big Bore 372 with a Meteor brand 064 piston. I used OEM 064 wrist pin and clips. I used that saw on a fuels reduction job for BLM over in Lakeview, OR, for about 400 hours before selling it on Craigslist. The new owner contacted me in April, '12 to say that the top ring had broken but the cylinder and piston were unblemished and he was re-ringing it. He's an occasional tree-service guy out of Grants Pass.
4.- I built and traded a Big Bore 372 to a member here, also with an 064 piston and rings (OEM) for use on his farm and for firewood. That was in 2010. That saw is still running.
5.- Back in early 2006, I built a big bore 046 for a guy in Maryland (furniture maker.) I put a couple hours on it before shipping. He got it, ran it for about 4 hours before it popped a wrist pin clip and wiped out the whole top end. This was the one experience that taught me to use OEM wrist pins and clips where applicable. I sent him a whole new top end and he installed it. Bailey's stood behind that one.