Zero.I have never downloaded anything hentai or porn.
with so much free to view online, what's the point? the furthest i go is book marking. if it disapears, meh. there's still tons more available, and new shit every day.
I usually keep the stash around 100+gb or so. Mosty taken up by the great number of videos, highest resolution doujin i can find, and a bad habit of never deleting stuff. Add some games, stuff from lurking the image boards and the boorus, and whatnot and it all equals a hefty bit of harddrive space. If i had faster internet it would be bigger i'm sure ;)
mine's 42 gb. mostly comprised of just videos. oddly enough, i've only watched ten of them and put off the other ones for some other time. when i'll actually get to them is beyond me.
25 GB of doujins, all categorized (pain to do, took a week almost).
89 GB of assorted hentai, in raw or translated form.
All together not that big, since I don't usually keep everything I download. What doesn't meet my criteria gets deleted, so what's left is some of the better stuff^^.
I actually delete my collection everytime it reaches 5 GB. I regret it each time because every time I restart I realize I deleted something that I know I'll never find it ever again. What a shame, but these things must be done in this crowded closet that I call my laptop.