Speak for your self.
JPEG is my final form for everything.

Suppose "raw" were my final form.
I used Canon 2007-2015, which means I would have to support at least one form of CR2.
I currently use Pentax, so I would have to support DNG.
But, then, what would I do with files scanned {I've used three different scanners, but none creates "raw".

I used Photoshop, but then moved to gimp; what if PhotoShop makes changes in PSD??

I could use TIFF, but as I noted earlier, TIFF differs between Win and Mac, and we did use Mac at one time.

No, standardizing on JPEG is simplest.

Are we sure that Jpeg's deteriorate? Files stored on hard drives and never opened never go away or degrade unless you store in the cloud or some place electronically not in your computer. Storage in outside sources do routinely run programs like defrag will cause some degradation because the file may be stored in several different places on your hard drive but then it would have to be run daily to cause any problems. I have never heard of file degradation due to opening a file and then closing it saving the changes. Maybe that was why they couldn't find Hillary's emails (file degradation she opened and closed them too much). Storage outside your computer will cause deterioration as the electronics involved send the file from computer to computer in little data packets that are reassembled at the receiving computer. I use external hard drives until I fill them up and then they rest on a shelf. The only deterioration they get hanging out on a shelf is that the metal and plastic in the drive will age in 10 to 20 years by then you should have a 1000 terra byte drive available that is as small as a thumb drive to transfer all your pics to from the external drives you have accumulated. I know I just got a 5 terra byte drive that is smaller than the 1/2 terra byte drive I have on the shelf holding stored info.
One last thought on deterioration ......
An old print if it had been processed properly might give you 100 years of enjoyment but will the new ink prints do the same? I have prints I made that are over 40 years old and still look good will my ink jet prints hold up as well?

To clarify... if you have not saved the original file, by saving the file as a different name, the changes occur to the file renamed, and are not carried to the original file. [Added] Renaming a file does not change the contents of the photo data; saving it under a different name changes the contents of the file with the new name.

If you do a checksum, there are half a dozen variants, your original file will still have the same checksum as when it was opened. If you save it as the original filename, without alteration, it will have a different checksum and will likely be marginally smaller. This will happen each time you open the file and save it. I don't know if this happens on loading or on saving the file, but, it does happen.

Do this with a *.tif, or *.png (without any compression) and the checksum will stay the same after loading and saving.

A fallacy: JPEG degrades every time it is oened (and as I was typing, others have posted). Why not do a test and see if you can tell any difference after 20 openings? And why would you open a jpg 20 times anyway?

The reality for most of us is we use jpg's to post online, email and send to bulk printing places such as Costco. There is no need for a tiff, especially if keeping the original file of layered edits - called psd in Photoshop and PS Elements.

There is no need for a rigid either/or - just keep everything if you have the hard drive space!