If I took a wild guess, I say 8 to 9 TB, maybe more. (My total porn collection: images, pdf files etc... has to be over 14 or 15 TB
I organize it by type of movie (mature, chikan, interracial etc..) or studio (Dandy, Natural High, Madonna etc..) If an actress has so many movies (i.e. Yumi Kazama, Ai Uehara, Reiko Nakamori etc...) then I'll organize it by her name (Whenever possible I have a jpg of the movie cover and a screenshot)
And if I go by the actress, it doesn't matter what studio the movie is under.
EVERY movie I ever kept is burned to dvd, unless it has a huge file size. I have binders that hold up to 320 dvds. I have an Ai Uehara movie that is 10GB, so unless I get a blu-ray burner, I won't burn it and it just sits on the hard drive. I can convert it to a smaller size and keep the original large one. I rarely delete movies unless they turn my stomach (too violent etc...)
Things do change over time. I used to have Dandy movies in one directory, but then I realized there are different types. Interracial, chikan etc.. so I divided those, but they're still under my "Dandy" directory.
Sometimes I'll download a complete series of movies at one time, such as "BTC" (Between The Cheeks)
I use torrents. I tried direct downloading and I hated it. I keep torrent files of everything I've ever downloaded (movies, music, tv shows etc...) and I burn that to dvd. (I have thousands of torrent files)
Of course I don't complete every download. Some stop at 50%, 80% etc... If a file stops at 99.9%, I'll copy it to another directory, give it the appropriate extension (avi, mp4, mkv etc..) and if I can see the movie with no problems, then I'll keep it. I use utorrent and leave it on for days at a time and I get one movie after another.
Another way is to go to one of those free JAV movie sites and just download them with your browser. You need an extension to do it, but you can. Some of the movies aren't good quality though. I have video editing software and if I have the time, I'll put together a personal compilation of my favorite actresses.
I used to be able to fit 4 movies on one dvd. But now, some movies only seem to come in hi-def and weeks or months later, they come in standard definition and I don't feel like downloading it again.
Sometimes, one movie can take up a whole dvd. Or someone will think they're clever and upload a movie as an .iso file that you'll have to convert. Or you get movies with the wrong titles.
Blank dvds aren't that expensive. ($22 or so for a 100 pack)
Both of my computers have 6 usb ports, 4 in the back and some of my external hard drives have an on/off switch, so that makes it easy. I can keep the drives out of sight. My big screen tv is 4 feet away and I have a hdmi port from the computer that connects to the tv, so sometimes I can watch the movie on a big screen. I'll use software like SMPlayer or Daum Potplayer. You can play your favorite scene on a loop (A-B) and also save vidcaps of it.
This is a labor of love, but I enjoy it. Recently I bought a 5 Tb hard drive. I'm thinking of getting a few more and then I'm going to backup ALL the stuff I own (not just JAV), back it up on external hard drives and put them in a safe or safety desposit box ($25 a year at my bank). So if they're destroyed somehow, I'll have a full backup.