My Deja Vu preamp and amp and Yamamoto Dac would all qualify. I’ve had my speakers also for 9+ years original JMlabs Micro-Utopias, but can’t say I won’t replace those eventually.
End of the line products.
I'm interested in those products that you've found "End of the Line", meaning no reason to keep searching, you've been satisfied with this product for 5 years, and see no reason to keep spending up the equipment ladder. For me, Essence Amethyst speakers, and Essence pre amp and amp now date to the 1990s.