MY PCs are at Rank 2 and are already hovering between 5 and 10 IPs apiece. I have no idea how it is possible, beyond breaking all laws of probablity, to have 18 IPS at Rank 6. 
(Unless some were removed with XP)
How Insane and Corrupt do you really become
You can be lucky…yesterday at the game I received 3 insanity points and 2 corruption points. I was VERY lucky and I had to burn one faith point not to get a maligency…
Our most unfortunate group member received over 15 insanity points and around 5 corruption points…
That was a result of our psyker's activity…5x psychic phenomena. Until yesterday we were very lucky…
Insanity points usually dribble in one or two here and there. When the psyker pops or when you start encountering daemons and stuff they add up fast.
So far my party hasn't dealt with a lot of horrific stuff… yet… they're still peeling back the onion layers and are starting to get at the creepy center, but we can always rely on the psyker to slowly pour IP into the party.
Just stepped on rank 5. 27 CP 9 IP.
Yes. I am a psycker.
I rolled a 91 on the perils of the warp table, resisted possesion got 4d10 CP. 
Except when it's the psyker's fault, I try not to make my players roll Insanity too often for what I would call "cinematic moments", when it was pre-established that they would encounter something horrifying enough. I prefer to make them roll Insanity as a result of their action. I think it's more significative to give Insanity to a player because he stabbed someone 50 times until he was just a chunk of meat, than giving Insanity just because he saw a chunk of meat that was someone before. But then again… Jaded is there for a reason and there is still the posibility of allowing the player to spend XP to recover sanity or letting them lose corruption if they destroy an unholy artefact (but those are kind of house rules). There is a lot of options in the end. I think as a GM, our role in this game is to make the players feel like they are on the edge, while not giving too much Insanity/Corruption to prevent their characters from being removed from play, but still punishing a player if they went and did something they knew they would pay for, exemple: Reading a Chaos book knowing that it would corrupt him (give less if it was necessary for your story, and more if it wasn't)