If it may help : I like to store for 10+ years top vintage champagnes, but only the kind which are developped as a wine (i.e. with a strong structure, not only chardonnay but a big portion of pinot noir or meunier). Usual names : Bollinger RD, the "emperor"; Cristal, the "king"; Selosse, the "prince"; Alfred Gratien, the "bishop". But be aware they will develop in time a very nice (for me) oxydation which I just love. Some people hate that. To give you an example, I still have in my cellar, in magnum (the best size for champagne) some Bollinger RD 1964. Magnificent ! If what you prefer in champagne is finesse, light, bubbles, freshness, (like 90 % of the champagne) do not store them, just drink them. And always keep a bottle in the fridge in case of an emergency. No harm, whatever you may read here and there. And do not hesitate to try one day the very good italian sparklings such as Ferrari (cuvée Giulio), Ca del Bosco and Valentino brut zéro : they beat quite a lot of french products ! If you think to be prestigious and go on Dom Perignon, choose the 90 : an exception of high standard under this name.