I never mill myself to death with tropius. i use it in 3 or 4 decks and its always just good. Either just attach another energy or keep your hand 6 cards or higher. Only time i ever feel like i would mill myself with a returner is with togekiss. That thing has only 1 attack and its more tempting to use since it does 30 damage rather than 10. Tropius milling you to a loss is like tropical beach milling you to a loss. Its just not going to happen. Once you get everything you need you probably wont be using it for drawing purposes. Besides with 1 retreat cost, if you can attack you can retreat to something else, this case dragonite. And 2 energy is at least 20 damage. might as well you that over return.