If I may suggest something, how about the older a deck is and wins, the rewards are increased. (Perhaps more money won for the deck maker and more ranking boosts). This gives some kind of "hope" for older decks, because they already have the handicap of age. It could be either a base addition (like +x extra electrum per win, x being number of days up), or maybe a multiplier for the increase. (days 1-3 decks have a *1 multiplier to won money, days 4-6 decks have a *1.5 multiplier, and 6+ day decks have a *2 multiplier).
