You make some great points, and I agree that one should take their time when considering whether to dispose of them. But I think it also depends on the type of journal, and here’s where I perhaps could have added more clarity. I have several journals I write in, all for different things. There are quotes, and a book of story ideas. Those I keep.
One of the thoughts I had when I found my old stash was that I could mine my life story for more article ideas, but for me, the pain was too much. It’s been almost two years since I tossed them, and I have never regretted doing so.