The skill Conceal (493508) causing buff Conceal (503753) and all other priest fary skills like Devotion Halo (499966) causing Devotion Halo (623016) have a buff time of 15:00 minutes but this duration is not shown.
This leads to the issue that player activate those buffs but after several time the disappear and the fairy dies in boss fight because it is not concealed anymore.
Probably this is a localization error with missing duration time 
Wait wait wait. I already wrote a ticket to support in september that buff from fairy disappears after a while and i have to turn it on again. And they fixed it with patch 10.0.4.2025 Link
My matt buff from priest/rogue fairy is always on. It disappears only when i'm too far away from my fairy and that's only because fairy is still a little too slow.
Also my fairy never dies during boss fight cuz it never comes close to the boss. When i summon it at the beginning of the ini (turn on conceal, matt buff, turn off counterattack) it stays there till the end.
I haven't checked other priest fairies maybe it's just p/r working, I dont know 
Alright, thanks for the answer, I will check again! 
Did not notice that change in patch notes, maybe I remembered wrong and perception in the last weeks was wrong 
I just checked priest/knight fairy and its buff disappears indeed.
priest/rogue buff doesn't. priset/scout doesn't either.
