follow the math. If you get a match every 30 minutes, that's 48 matches/day. If your deck is still in play on Day 6, (and the top decks all are), that means they've gotten 6*48 matches.
In reality, most of the top decks (at least in Platinum) are merely approaching 100 matches. Divide 100 matches by 6 days, and you get less than 20 matches/day, or less than 1 match/hour.