I took a closer look at the e-miles terms. Here's what some of the fine print reads: e-Miles miles are deposited in 500 mile increments with overages rolling into the next quarter. e-Miles reserves the right to change the increments and/or frequency of deposits.
It's not clear whether this implies they'll only deposit one 500 mile increment per quarter or whether it's in 500 mile increments until you drop below that level.