Well, I still see ads for Raid online all the time, so they are still spending money on new player acquistion, and if you are trying that hard to acquire then logic would dictate that you also want to retain.
Yes. But they aren't interested in f2p.
Retention of $$$ is always a better metric than player Retention
$$$ being expected future value
I'd hazard a guess anyone not spending in 30 days is considered a 0. Obviously they have a more complex algorithm, but even the most sophisticated models can be OccamsRazored with 2 or 3 variables with 90% accuracy :)