http://www.gpugrid.net/forum_thread.php?id=2422#20300

We are introducing the possibility for users to select between shorter (acemd2, approx 4 hours on GTX275 cards) and longer (acemdlong, 8 to 12 hours on GTX480) tasks. Simply go to your account preference to select which applications you want to crunch for. Long task are of course credited higher, but GPUs with less cores cannot simply compute them in time.