My ever longest battle was 32 turns against fake god Miracle(I won^^).
Having the deck around 30-35 cards let you be almost sure to have key cards in the starting hand(if you have at least 5 copies of it).Decks with more than 35 cards need card drawing to be reliable.
If you like life-dark sinergy try out andrenaline-minor vampire-nightfall
When a creature has 3 atk it deals 12 damage with andrenaline and vampire also heal you for 12.
Drain life also could be useful killing opponent's dragon or other else!