Why do you need a few Kindles and also a Kobo? Are you keeping them in different places and don't move them? I only have the first Paperwhite which I carry along, it's 11 years old already and it still does the job. The battery keeps up and I was probably lucky to not have noticed any hiccups.
I read several types of books, multiple hours per day: reflowable fiction books, PDFs, books generated from my Markdown notes… I’ve got a Paperwhite, a Scribe and a Kobo Forma, but I’m still searching for the perfect e-reader.
The Paperwhite is too small for PDFs, but great for fiction and portability. The Scribe is excellent for PDFs, but it makes my books disappear sometimes, and it does not work well with sideloaded fonts. The Forma is a middle ground in terms of portability, but its battery died after a couple years and nowadays I only use it near a power outlet.
I use a combination of a Kindle Paperwhite Signature for novels and mainstream books. THen I use a Remarkable Tablet for PDFs, research papers, my own notes, etc.
I find it to be a good combination. Like you said, the paperwhite is amazing for laying in bed at night (really like the backlight) or on the couch or traveling to read. But it is too small for PDFs or serious notetaking. The Remarkable is perfect for those things. The remarkable also gives you full control over your files to do whatever you want. You can connect it to Google Drive, Dropbox, OneDrive, etc and/or just manage files directly on device (plug it in via usb-c and it shows up as a USB mass storage device).
The two tools compliment themselves nicely. Just my 2 cents.
My wife is a pretty voracious reader and has 3 active Kindles that I believe are mostly segregated out by genre/collection. I wouldn't be surprised if this is as much for convenience as anything else, I don't use it much but Amazon's library management and navigation on the Kindles has never impressed me.
She's also one of those folks who sideloads with Calibre as well as purchasing through Amazon.
I think you just naturally end up with that because the things appear indestructible. The first ever kindle I bought (dunno how long ago, it was before paperwhite, so more than 11 years) still works without issue. Even retains all the music I put on it 14 years ago when it was still an experimental feature.
I think the only thing that has been discontinued is the free 3G internet all over the world that they apparently figured was too expensive.
I _loved_ my Kindle Voyage for its adjusting backlight and glass display.
I wish it were less destructible! I upgraded to a Paperwhite (2021) when the Voyage's power button broke. Water resistance is nice, but having to get the "signature" edition for a light sensor and an easily scratched plastic display is quite disappointing.
