I have researched this CO thing a lot on these boards and other forums. No one really knows which is very confusing. All I ever see is the fact it will remain for 7 years and then fall off at 7.5 max. The whole squirrely thing is the counting of how the dates are 30,60,90,120.150 etc and for each of those we get dinged. The 30 fades fast, the 60 a bit slower, but we get hard on the score for the other dates when it all on the same account that went into a CO status. It confuses the consumer that is for sure.
I have definitely improved my scores from 544 to what it is now from all the help on these boards.