I am currently running a Vaesen campaign; I am 37 sessions in, with each session being about 4 hours. And still ongoing.
I have opinions. My first one being that the Vaesen iteration of the YZE was clearly not intended to run campaigns this long.
If you are planning to go for a long-term campaign the following are a must:
Double the XP for PC's and castle upgrades after 6 sessions. In the first six adventures you likely encounter a new vaesen each time, which should give the PC's and advance each session. This will give them a little turbo boost to their survivability...
This would let the Players get a few skill and talents to round their PC's out before advancement slows down. And even at a slowed rate they will get an advance every 2-3 adventures on average.
Even then the d6 system is harsh for chances of success, and it can be swingy. PC's need to roleplay out as much as they can, and take advantage of all the equipment, facility, and services bonuses that they can. The dice are not the PC's friend.
The 'annals of the society' should be the #1 first upgrade they get for the Castle. A Must Buy; +1 XP per adventure. If your players don't notice this, point it out. Or they will be missing out on a lot of XP until they get it.
As PC attributes cannot be advanced RAW; there is no point in making middle aged or Old PC's. Their decreased stats will eventually catch up to them. Fear, and Critical hit recovery rolls are 100% attribute reliant, good GM's don't let their players create gimped PC's.
Talents:
'Safety in numbers' a must have for Fear tests. They will not like failing Fear tests. Ever.
If the PC is going to fight 'Defensive' is a must have. Then Fleet-Footed asap.
Holy Symbol is also a must have for the PC with the best Inspiration.
PC's will also want to look at anything that reduces Action penalties, and/or Condition penalties for rolls, for their character concept.
They must also memorize and burn into their soul the fourth sentence of the first paragraph of p.22: "You can use your memento once per session to heal two Conditions."
Observed issues:
Combat can be swingy/keystone cops when it happens if both sides have equal die pools due to the low success rate.
The instant you push in Vaesen you immediately give your PC die penalties for all further actions of that kind. Which you will likely carry for the entire adventure. Especially if you have already used your momento heal.
Pushing in actual play is only done in desperation. I did a slight rules mod to fix this.
To use the Medicine skill requires a Entire Day of Treatment. In the overwhelming majority of published adventures put out for the game (and I've ran nearly all of them plus quite a few from DTRPG), a day off to heal means that the Vaesen will likely kill an innocent, and the other PC's will be at a big disadvantage.
My players twigged to this quick, as a result the medicine day of treatment is never used in actual play.
Getting damaged all the way to Broken, then having someone make a medicine skill test is literally the fastest way to heal a PC to full health in the game, RAW.
All that is why I now allow a first aid roll like in the blade runner rpg.
Hiding clues in published adventures behind multiple successes is nonsensical. Don't do this, spread them out in different locations. I wind up modifying a lot of adventures because of this. Not a big deal as I yeeted the whole Linnea plotline from day 1, so I have to slightly re-work adventure motivations anyway.
The Critical hit charts have times for mental and physical consequences to take effect that are completely irrelevant during actual play. So I redid it.
I also adapted a version of the shift system from Blade Runner, 5 instead of 4, to keep investigations moving, with time as a resource. Works Fantastic.
I'm here all year kids, standing ready to dispense wisdom and practical advice...