Cognac (along with most liquor) does not age in bottle, so all the aging is only when it is in cask and stops once it is bottled. In fact it will be slightly worse after 20 years in bottle than when bottled, so you didn't get any aging or improvement during those 20 years (unlike wine). Presumably that means your 50 yo cognac was 30 yo -- which would not be labeled Napoleon typically. There is no legal definition of "Napoleon" except by convention it is usually the grade better than VSOP and worse than XO. This generally means it is about 10 yo (with maybe 1% 30 yo content at most), though the legal requirement is a mere 4 years .... and some are that young and coarse! It is very much a "buyer beware" though the name brands try for consistency.

Some of the US and Australian brandies are as good or better than French cognac and often much cheaper. Try Christian Bros. XO for example (not comparable to a French XO, but also a fraction of the price).