I love Dior Airflash Foundation. The coverage is beautiful -- but I only use it once in awhile, because if I used it on a daily basis, it would cost a fortune for me. I don't know how long it would last if used on a daily basis, but I go through it far faster than any other foundation I use. I started using it about a year or so ago, and I'm on my second can of it, just using it on occasions. But, I do love it.
Edited to add that my friend who works in cosmetics recommended spraying it on a Dior brush, and I buff it on that way. I have never used it any other way, so I would think that would waste less than using it just by spraying on your face.
Janice