It really depends on what the achievements entail. I believe I only have the Platinum on God of War 2 and 3 (which can be earned only going through each game once) and Assassin's Creed 2, which I got after getting the DLC at which point I finally collected all those feathers.

Essentially, if I find an achievement ridiculous or too time consuming and I could play a different game, I move on. Demon's Souls is a prime example, where you have to beat the game 4 times to get a couple of the trophies, and it's already a painstaking game the first go through. Love the game, completely not worth trying to get the Platinum.

Oddly enough on the other hand, when I played some 360 games on my roommates 360, I had 5500 points and only played 6 games (no DLC). I got as close to maxing all those games, except for say, Modern Warfare and the stupid Plane mission at the end, or Lost Odyssey and opening every chest.... 980/1000 for both.

THE JACKEL