It looks like you'll have until Dec. 23 to activate distributor rx's and get paid, whilst you can start buying through Echo on Nov. 2 if you don't already also get through Echo. If you already get through Echo as well as a dist. (which should likely apply to most), you can drop off of getting from dist. immediately, to minimize dist.-acquired inventory overhang come Dec. For those who are dist.-only, this might be a trickier question- if you can't actually start with Echo until at least Nov. 2, you may have to more carefully calibrate for having enough gear on hand to do business without it being more than you will get activated by Dec. 23.
Compounding that may be the question of dist's continuing to stock deeply enough to get you all you'll need through the end of Oct. Presumably Echo will take back any of their unsold inventory, but who knows? What incentive does a dist now have to make sure you can get what you need?
Time now to remember all of those past dist's. I started with CSS and Skywalker for C-band, then Skywalker for DiSH. They parted ways a long time back.