According to the T&Cs, instalments are available on the annual (and quarterly) plans. I would guess the difference is that in an annual plan, you are committed for the year, while monthly can be cancelled after a month...
Had a read through the FT thread. Some butt hurt Lifetime Diamonds over there. I am probably that far away from LD that it doesn't affect me, but I don't get the negativity. Maybe down the track if they remove something, but gee, they seem upset
In the case of Velocity, it is a once off benefit. Given it started years ago, I wouldn't think there are huge numbers coming through that path anymore.