EDIT:
I realized I should probably have been clearer, 40TB (for another week or two, anyway) is just my Anime library, the part I mostly care about - I rip TV show/movie BDs mostly for family/friends, with the exception of things like Game of Thrones, The Expanse, and the like, and slightly older shows like the various Stargates, Babylon 5, and the good Star Treks. Movies (for myself) are mostly classic Sci-fi and Fantasy, as well as the guilty pleasure of the Marvel movies when my brain needs to shut off.
… Yes, I’m a huge geek 
Everything else is family and friends, ripped from BD, or encoded from the best WebRAW or stream-cap I can find if still on air (I have A LOT of BDs gathering dust in a storage room…). On-air shows usually get AVC high@L4.1 or higher, depending on source quality (so, sometimes lower), with audio depending on what I have to work with. I care less about those, since they get swapped for my own rips as soon as the BDs are out, anyway. Haven’t really checked the grand total in a while, but I moved to 8TB drives a few years back, and still have 5 open bays in my 25-bay case, so not that much.
Well, most of my library isn’t in an old, inefficient encoding, but rather specifically encoded for the type of media, which means a lot of “Hi10p” h264 10-bit encodes with FLAC audio, a format that never really caught on with the general population, but is great for higher-quality, lower-size anime encodes, as well as 10-bit HEVC/h265 encodes with either FLAC, DTS-HD, Dolby TrueHD or Atmos audio, where the audio is every bit as important as the video.
Reencoding already lossy encodes, especially to an older, less efficient standard like basic h264/AVC, will result in a major quality hit, especially since it isn’t capable of encoding color and visual details nearly as efficiently, often requiring massive file-bloat for minimal quality increase the higher you go. I’d never outright replace my files with lower-quality reencodes, since I specifically try to get the best quality I can, so that would be putting the horse before the cart.
Most of my personal media consumption is in my living room, where I use an HTPC that plays my files directly anyway, and streaming outside the house is limited to family and friends (I’m not trying to compete with Netflix), or when I’m traveling.
I just can’t see purposely decreasing the quality of your media as a good solution - sure, basic h264 will play on a toaster, but that’s the same place we were at a decade ago with DivX/XviD; there’s a good reason no one uses those anymore. h264 hardware processing became common, resource-friendly and affordable, and before long, the same will happen with modern codecs (with the likely exception of Hi10p, which just never saw wide-enough adoption).
It took me ages to replace all my old, low-quality AVI versions (usually using DivX + MP3/Vorbis) with decent quality h264 + AAC/FLAC MKVs, which is still about as good as you’re likely to get out of a DVD source, but I definitely don’t want to have to go through that again unless I have to. h264 + AAC is fine for airing shows, but once you have the Blu-rays, I feel like making a lesser encode (or worse, reencode) from the source is kind of wasting the money you spent on them - unless you make multiple versions, but then you have the space issue, and I’ve been going through 1-2TB a month as is lately, and, even with a gigabit connection, any more and BackBlaze will start to intrude on my waking hours.
I think I’ll just have to upgrade my server eventually - I’m running a set of old E5-4620s, and while they’re still holding up (even slow processors can still kick some butt in a 32C/64T config), being stuck on PCI-E 2.0 and DDR3 is definitely a pain. I’m currently broke from medical bills and the lack of income that accompanies being bedridden for months, but, assuming I’m back on my feet by next year (and, dear God, I hope so), once I’m back working, maybe I’ll celebrate by irresponsibly blowing my renewed income on some crazy Ryzen 2 Epyc-based server setup; the idea of being able to have the same number of significantly faster cores in a single processor as I currently have in four is incredibly appealing, even if the higher-clocked, lower core-count versions might be a better choice. I suppose it depends on how many I can stuff in there (haven’t really looked all that closely, as I’m spending most of my time in a bed-locked zombie state).
) per unique media to build up a hashtable of distinct show information objects and build a set of rules to drive your ffmpeg convert as: