Madeira is a fortified wine (18-20%) matured in the cask where oxidation and reduction processes happen. Due to the oxidation (constant contact with oxygen inside the cask) Madeira wines will be very stable and have a huge lifespan after opened.
Bottles of Madeira wine should be stored in an upright position, the main reason for this is that the wine can 'outlive' the cork, as madeira wine can last for hundreds of years. Bottles should be kept out of direct sunlight in a location without great variations in temperature.
Madeira does not require decanting, although this is always a good idea for old Vintages. Use a good cork screw, or if the cork seems fragile use a 'butlers thief' to ease the cork out of the bottle. Wine should be served between 60ºF and 64ºF, depending on the age and style of the wine.
Madeira stops ageing once it is bottled. The complex characteristics of madeira wine is the result of ageing in oak casks under special conditions. The age of the wine is equal to the number of years it spent ageing in barrel.