Unlike expensive (and some say very over priced) champagne, Prosecco is usually produced using the Charmat-Martinotti method. This is where the secondary fermentation takes place in stainless steel tanks. Making the fizz this way is easier and also less expensive to produce.
A huge 150 million bottles of Prosecco are made in Italy each year! Unlike it’s expensive cousin champagne, Prosecco does not ferment in the bottle, and this means that it grows stale over time. Where as champagne gets better with age, Prosecco does not. It should be drunk as young as possible, ideally within three years of its vintage, although high-quality Prosecco may be aged for up to seven years.