I noticed that if I booked a round trip as two one ways using my AS Visa Check Card, I get a 1000 mile bonus for each individual purchase, effectively giving me a 2000 mile bonus for each round trip instead of 1000. The first time this was unintentional, but after discovering this trick I think I might start booking all round trips this way. I'm still quite new to being a mileage junkie, so before I made this a habit I wanted to check if there was some big reason I shouldn't be doing this. Are there any major drawbacks to booking each leg of a round trip with separate purchases?