That's one of the drawbacks of DOCSIS 3.0 too (channel bonding). Reason being, that, if any one of the bonded channels goes out of sync, I read it has to retrain all of the channels with the head-end. So just one out of sync == retrain of all channels. Which, due to multiple channels and DOCSIS 3.0, takes longer than DOCSIS 2.0 I think too.
But when it's running fine, it runs faster.
Edit: Channel bonding is like a RAID-0 array of cablemodems. That's why it has to retrain if one goes out - just like losing the entire RAID-0 array when one drive goes out.
Good description. I had the older 6120 modem which worked great, until Comcast started supporting 4channel bonding in my area. Suddenly, I was getting dropped every 10 minutes. Techs were out several times, but nothing really helped. CC insisted that the 6120 was the problem, so I replaced it with a 6121 which was listed as fully supported , but I was still getting dropped hourly.
Finally, the HOA decided it didn't like the appearance of my cable routing, and a technician reattached the cable to the outside of the building slightly differently, and I had 3 months uptime without a drop. I believe the only thing that changed is the tech cut the screw plug off the end of the cable in order to move it, and attached a new one afterward.
The moral of the story is that a single channel will tolerate a marginal connection, but 4/8 channel bonding has to be flawless. The 6120 now works perfectly as well. Every time I have a problem the technician has blamed the modem, but in 15 years it has never once actually been defective.
I would only get the 6141 if you plan to have a connection higher than 150mb/s, because the more channels you have, the more opportunity there is to get dropped. In my area, 50mb is the top speed, and the 6121 works great.