I was able to get about 220,000 miles in a year using just 2 Citi cards.

I got the PremierPass Elite level with 15,000 bonus points, and bought about 6 tickets to Europe for friends. I ended up with about 75,000 Flight points and 5,000 purchase points from that.

Then I got the Diamond Preferred Rewards card with a measly 5,000 bonus points. This was when they still gave the 5x points for gas and groceries though. I was still in college last year, and I volunteered to buy all the alcohol for my fraternity. At about $2000 a pop for each party or football game, I got about 10,000 points per trip to Safeway. I did this about 10 times in the year and got 100,000 points.

I know many people say this doesn't/isn't supposed to happen, but Citi matched my PremierPass flight points to my Diamond Preferred purchase points, which gave me full use of my 80,000 flight points, bringing my total to 200,000. I think something may have slipped through the cracks when they did that transition to the new ThankYou rewards system. Maybe it was because I consolidated the two cards on my ThankYou account?

Then, with rent and other daily expenses, I racked up another 20k, for 220,000 points in a year although my annual income was only about 20,000.