I have started to look into getting a FF miles CC. Reason is that I plan on sending my kids to korea every couple years during the summers.

But I have wondered how the miles program works with credit cards and earning them. I seen many of them with a bonus miles when you first sign up (25k miles, etc), and earning anywhere from 0.5 miles to 1 per $1 you spend.

Am I missing something in how you get rewarded and then use the miles for tickets?

Trips from where I am (LAS) to ICN is roughly 12k miles roundtrip. With say a bonus of 25k miles alone, that is enough for 2 tickets?

Is there something I am missing? I notice most cards do come with an annual fee (first year waived). Do the miles you earn ever expire? And I assume the best way to get miles is to use a specific airline program?

Also, how do the tickets get purchased? do you have a choice with FC, Business, Economy?

I just wonder because it seems like a big bonus (way better than a reward such as 1% cash back, which to me, seems like it would be way worse than FF mile rewards?). I mean, 25k miles bonus, and a trip to korea is 12k miles, is enough for 2 tickets, and that could easily be $3000 if paid for myself?

There has got to be some conversion or silver lining in this that I am missing?