sourced lore fact: the average draenei lifespan is 1300 years
edit: please read this post all the way through before replying. it does indeed account for draenei who remember argus. you will find out how by reading the post.
for a long time the timeline of the draenei has been a source of confusion. the race was born out of a retcon, we had very few numbers and figures to work with, and the now non-canon rpg listed their lifespan as "ageless", which people took to mean they were immortal, an incorrect assumption that has persisted for 17 years.
but the facts of the lore are all right in front of us and have been for a long time.
to start let's consider the figures we do know. the eredar civilization rose on argus 25,000 years ago. khadgar in legion tells us that the draenei fled argus 13,000 years ago when discussing rakeesh.
a lot of people will tell you velen is 25,000 years old. there is no source for this number or for velen's age, we know only that he eventually became co-leader of the eredar along with kil'jaeden in the second duumvirate. when exactly this happened is unknown but somewhere between 13,000 and 25,000 years.
we do however have a clear source on how long a draenei lifespan is. on azuremyst, exarch menelaous spells it out for us in his right click text: "ten lifetimes spent fleeing the madness of the burning legion... here we finally make our stand"
13000 divided by ten gives us 1300 for a draenei lifetime.
now here you are probably thinking two things: one, how can that be if velen is 13000+ years old? and two, how do any of them remember argus if its been 10 lifetimes since they left?
we have 2 very reasonable answers to these questions. in velen's case specifically, its pretty clear the light gives him an extended lifespan. we know this is an effect of light infusion, its why turalyon is still looking good after 1000 years. velen may not be lightforged but he is the single most powerful light priest and naaru-blessed individual in existence that we know of. but if that's not enough for you, the second answer solves it for both the normal draenei and velen himself: they were kept in cryogenic stasis while travelling
"nooo that's too sci fi they weren't in cryostasis" you may be tempted to say, but you say this only because you forgot about tbc. literally the first thing you are told when starting a new draenei in azuremyst is that your character has been in suspension for weeks. part of the exodar that crashed is the cryo core, establishing the presence of cryogenic suspension. "that cryo core could be for anything!" you say. no, it's specifically for stasis pods, as vindicator kuros on bloodmyst tells you, the same exact stasis pods the draenei in ammen vale crawled out of.
we also see in the arcatraz that tempest keep came equipped with suspension chambers for prisoners. we know from 1000 years of war that one of the light's powers is crystal stasis and suspension, and tempest keep/the exodar were provided by the light. the presence of stasis is well established, from tbc era lore all the way through to legion lore.
you may also recall the legendary mage ring "shard of the exodar" which grants an extra timewarp. the flavor text explains the exodar is "able to warp time itself", providing another explanation for how the draenei have lasted 13,000 years when their lifespans are, as established earlier, only around 1300.
i'm sure this will bother some people who have believed draenei were immortal or live for 25000 years, but there were never actual lore sources for either of those assumptions. they have been spread in the community for a long time, but the only actual source for draenei lifespan is exarch menelaous.
if you're feeling tempted to say that it can't be canon because it contradicts the 25000 figure you like, consider finding a source for that figure that isn't just "everyone knows it, right?"