I work with Interstate Batteries, and we are a big Optima dealer since Johnson Controls owns Optima.
I have a redtop manufactured in December '08 in my Chevelle that has worked perfect. I bought it brand new.
My Xj has an '08 red top as well, but I didn't buy it new. I picked it up somewhere as a supposed core, charged it, took it for myself and it's worked perfectly.
As far as dating a battery, find the date code on it. Theres a few variations. Should either be stamped into the top and can be faint and sometimes kind of hard to find. Usually in the corner area though. If it says some like 8LAF, then it was manufactured December of '08. You just need to pay attention to the first two, a number and letter. The number indicates year, and the letter coresponds with the month. L is the 12th letter of alphabet, therefore L indicates December
The other kind that Optima used to use is a Julian date code, and it's stamped into the side. If you looks on the side of the battery and it says 7145, that means it was manufactures on the 145th day of 2007.
I don't know when the plant changes occured and all that, but it seems like a lot of the Optima's I warranty are from around '07 - '08ish. However, you also have to remember a lot of customers who buy them don't know how to charge them. AGM batteries require a different method of charging then a regular lead acid. But, if a customer doesn't know that and it doesn't work out for them, they bring it back claiming 3 yr free replacement. Store obviously obliges to customer which is where we come in because we gotta take care of our customer.
Last couple of side notes: Date codes like 7145 or L7 Could also indicate a year of 1997, so use judgement, if the battery looks ancient, then it's probably older then 2007. Also, the letter/number date code works for all your batteries, it's a universal type thing.
Hopefully that wall o' text was helpful to somebody
