Most wines are now sold ready for drinking and do not need to be left to mature, however, most will improve in flavour if kept for a while before drinking if stored in the right conditions, with the exception of very light-bodied or cheap red wines.
Given the right conditions the length of time a wine should keep varies with its type and year of production. The weather affects the acidity and tannin content of grapes and these, in turn, affect the way it keeps. An ordinary wine from a good year may keep as long as a good wine from a poor year. As we are not all wine experts the best idea is to seek help and advice from a good wine merchant.
Some rough rules to remember are that not all wines improve with keeping. Secondly, plonk stays plonk no matter how long you keep it and keep in mind that white wines mature faster and fade faster.