Well, the »turtling« will turn into simple real life time economic behavior: from mid game on, the pure number of ufos is growing dramatically. You will have enough to do, just shooting them down. Landing at every landing site and doing the mission will take weeks in real life, until you reach the final goals of the game. And you most definitely don't need 10.000 score at the end of the month. 2000 or 3000 is quite enough and from midgame on, can be achieved quite easily, just by their sheer number. Don't pik fights you will have to expect defeat (excluding terror missions, at least show up there) and you will have a rather smooth ride. Shooting them down over water and only going to actually interesting missions, chosen for some reasons (landed ufo for Elerium would be one of those reasons) is fare more economic in terms of playing time. So some of the turtling tricks, like shooting ufos down over water, can be useful also in terms of game experience: One less white cross on the map, that nags you to wipe it out now. Base defense missions will come on their on, as well as terror missions (if you can, rather shoot down the terror ship). If there's a battleship full of floaters, it might be a target, if it's landing somewhere, while you are short on Elerium. But why bother damaging you own crafts? Land there with them. Infiltration missions of battle ships you can't do much about, similar with retaliation missions. The rest isn't really dangerous.
