I have experimented with these bateries for years now with different end results. Same battery type used in two different cars.
Car 1:
The same red top optima in the Z three years now. During winter it's pulled and put on a shelf indoors with no tender ever for 4 months. Spring, a quick charge, goes back in the car enough to get the car up on jacks till usually August. Then about a two months of driving (700 miles average) and the cycle reapeats. Impressive performance. The deep cycle abilitly is remarkable!
Car 2:
My 95 year old grandmas (yes she still drives!) 1991 Lexus 250. This car is never driven more than 10 miles a year for the last 5 years now and stored in a unheated garage. This car has required an new red top optima every year and they are not cheap.
The difference to me is any battery constantly conneted and not charged will never last. The electrical system in the lexus is much more complex than the Z of course. That being the case the lexus should deplete the battery quicker if tested side by side? It appears it does just that though already. Also the Z car is never left more than a month with termials hooked up to eliminate the chance of fire and stored indoors during winter. Tempreture might be small factor. My thoughts are the odds of electrical resistance difference in each cars particular wiring system is much more of the issue than just getting unlucky during the manufacturing process.
(that was too much info, i'll shut up now)