C

Easy to Earn and redeem.

The one factor that lowered it is the one year expiration unless you are Elite or an A+ Visa Cardholder.

If they want to improve their grade, make them non-expiring as long as there is some type of activity. Three years of inactivity they would evaporate.

As previously mentioned, some fares are so cheap, spend the $$$ and save the credits. I find myself buying a cheap coach fare, and using the credits on a long haul confirmed upgrade.