Is there anywhere that tells you what NPC's you lose access to at which rank? I am wondering about the non-shareable ones. The wiki has shareable NPC's but not what I'm asking about. Am curious how long flamehawks, blade harvesters, etc. last. Are matched NPC's ones that will stay with you no matter how high of rank you are, or do even they have a duration?

2200 you lose harvesters , TO troop carriers, and Dark arms carriers (and gain a new npc that gives similar drops)
at 1200 or 1600 you lose the stryll devastators that drop a scanning buff arti.

Those are the only "concerning" ones that I remember.

Crimson tyrant and stryll devastaters go away at 1200

Flame hawks never go away.
All the matched commons and uncommons, except blade harvesters, go on forever.

As far as NPCs go that can't be alerted.
Worry about
Stryll devastaters at 1200, they give the % scan boost and nothing replaces them.

Troop carriers at 2200
Terraformers are still supplied by the dark mass carrier but at a much worse rate.
Quasi spacial expanders aren't dropped by anything else.

Devastators, yes... but the Tyrants are gone before that, 1001... it's been 87 ranks since and only gotten 3 crimson amps from hawks :/

So all in all it looks like you lose more NPC's than you gain. Wouldn't that make hunting the legion mission NPC's easier since there are less to choose from, or does that really have no effect?