Some of the earlier bottlings of Black Stump from the 1990s are offered in a maintained state.
Traditionally this sort of process has come about from use of the natural cork closure.
Some wineries keeping special historical wines for many decades will re-cork them from time to time. This might also include topping up if the levels are down. In fairly recent times Penfolds have offered the "Grange Clinics". People bring along their aged bottles of Grange and a winemaker opens the bottles, checks their condition, tops up if necessary with a more recent vintage, and then recorks.
Due to the bottle design, when a cork closure has been used originally, then a cork must be used to reseal when maintained. There are a number of choices in cork for today's winemaker. A matured wine is in a delicate state so the process is carried out very carefully with minimal disturbance. The wines remain on any sediment that has been thrown over time, so they are still best decanted when eventually opened to be drunk.
Although the Black Stump bottles are still youthful, and the fill levels are good, this is more of a "preventative maintenance", primarily for purposes of guaranteeing a consistent product. It ensures that all wines are in a good drinking condition. If some people want to cellar the wines for longer, then the new closure will facilitate this also.
For the maintained Black Stumps the "Diam" cork has been selected. Any problem of cork taint, failure or degradation second time around is at the least minimised, possibly eliminated. This closure does not require to be kept moist by lying the wine on it's side. Therefore, all things considered, it is recommended to store your maintained Black Stumps standing up. The date of maintenance has been notated on the label.