Originally Posted by CO Insider
Good question, Mary2e. For roundtrip tickets booked in multiple classes of service, you'll actually earn the credit amount for the highest paid class of service in that reservation. This means in your example (discounted coach in one direction, Z Class in the other), you'll earn the D/Z Class credit, which is 10 credits for your first activity and 6 credits for each repetition.
COInsider:
What if you have a round trip booked as 2 separate one-ways? I haven't received the Mileathon thing yet, so I can't say I've seen the T&C. I get the gist that it may only apply on RT (or CT or OJ) itineraries? In a market where one-way fares are cheap (e.g. LAS, BWI as restricted or Full-Y fares), I have a trip in that time frame booked as two OW records, as I couldn't predict the return at the time I booked the outbound. I guess it'll also give me an extra 500 continental.com booking points, now that I think of it...