Interesting question. There is no one answer because how the vehicle is used plays a significant role in the emissions system's lifetime.
I put a Banks iDash Data Monster on my ECODiesel because I want to understand the strategy of the regens. It appears a passive regeneration is used throughout the drive cycles but then, on my vehicle, every 900 or so miles the system goes into an active regen that takes about 12 minutes to complete and it can do it driving in city traffic.
After an active regen, the soot load goes down to near zero but slowly climbs back up where it will hold in the low 60% range until the next active regen. Apparently, the passive regen has some intelligence to it, at least it appears it does.
I did some searching on passive versus active regens and got quite the education. The current strategies should allow the emission system to last the life of the vehicle on par with catalytic converters. A lot of emission system maturing has happened since the old days (like 2007).
I've read on the Cummins forums there are hots hotters out there with a lot of miles (500K +) that didn't have emission system issues.
This is about it - there's not really a 'solid' answer on this because how you drive basically dictates the lifetime, much like every other part on a vehicle.
6.4 Hemis have a reputation for puking their lifters before 100k miles, some as low as 40k. My 2017 had 102k on it, and when they did a partial teardown (valve covers off, plugs out, bore scope, etc/etc) trying to figure out a rough-running (then no-start) condition they found no wear/play in my valvetrain. I drive about 60 miles per day at 55 mph back and forth to work.
6.4 Powerstrokes have a reputation for being grenades. My dad has something like 300k on his, and the only thing that's EVER been replaced besides oil and tires is the radiator, because the original design (and then first re-design) tended to have the tanks at either end crack and start to leak. Heck he even still has his original DPF on it. He still drives it about 30 miles back and forth to work every day.
The old 6.2 diesel GM used in the 80's didn't really have a bad rap, other than being underpowered. The one my dad had was replaced (4) different times, each time at about 50k miles. Once because the rear main dropped out, once because a glow plug broke off and grenaded a piston and sent a rod through the side of the block, once because he noticed a major lower-end noise and found the 3rd and 4th mains were no longer part of the block...and I can't remember what the 4th time was. My point is, based on that experience, he ended up with a 454-powered truck after that, that he took to almost 300k miles.
Back in the 90's, Mopar got a black eye because their transmissions tended to not last more than 60k. However, I know several people who owned some vehicles from back then who never once had transmission issues, and ran up toward 200k miles.
It is partially 'luck of the draw' - there are definitely some vehicles out there that get bad components. But there's a lot to be said about how you drive and care for a vehicle. If you don't hot-rod everywhere, and keep on top of your maintenance, there's a strong chance the vehicle is going to last you quite a while.