As some readers have pointed out, multiple entry cards are possible. On my last occasion going through security the officer, after reviewing my I-194 waiver and my I-94 asked if I travel to the US often. I said yes and to my surprise he said, "well, I'll give you a multiple entry so you don't need to fill out the I-94 each time. Is 6 months enough?" The best part about this is it speeds up my processing (plus I don't have to prefill my I-94 each time I travel). See the enclosed document scan, I'm good until the end of September. Wahoo!