With an experienced team you could possibly get a rhythm going, so that there is always somebody hitting infected, but this is difficult. With the new delay on melee, the harder campaigns become even more difficult, as it is no longer plausible to all sit in a corner holding down the left trigger. There are many glitches in this game, but they are slowly being removed.
If you have Xbox Live and the new 'Survival Pack', you should use that too for some variety.
Depending on how many zombie kills you are averaging per campaign, you may need to play campaigns an upward of 50-60 times. There are an abundance of achievements you will get for just playing through the game, and you may indeed get a few to pop up unexpectedly, which is always nice. With a good team of people, you can easily fly through this game on Expert. Left 4 Dead is not an entirely difficult game once you get into it. Does difficulty affect achievements? Yes. Do cheat codes disable achievements? No cheats. Minimum number of playthroughs needed: Many
Approximate amount of time to 1000 : 45 hours
