Not sure if any of these will make it to the BIFL level, but notable in today's "fast fashion" world:
I have several dresses from the Ann Taylor outlet that are 20 years old, and still look brand new. I remember purchasing them once I got engaged, thinking they would be good for my honeymoon. Never expected them to still be around, and they are rather forgiving cuts, so they still look good and fit, even though I've added some pounds over the past two decades.
Also from the outlet, I purchased a leather wallet from Etienne Aigner, roughly 15 years ago. I recently threw it away, but only b/c the leather had begun to flake off, and the second of the two snaps had become loose. Functionality overall was not an issue, and I highly doubt it's replacement will last nearly as long! I do keep an eye out on eBay for those wallets and purses, hoping to find a quality one that would stand the test of time.
My Kirkland non-stick cookware has also lasted the test of time, 19 years or so and still going strong. To be fair, I'm meticulous in keeping metal utensils away from them, and cleaning them only by hand, with a non-stick scrubber, if needed. Pretty sure that this was private labeled through Calphalon.
Corelle dishes - our daily go to, and they are awesome. A few years ago I found a similar version at Ikea, and I picked up a 6 pack of dinner plates, plain white. About 10 years and not a scratch or chip on them!
I did own a Kirby for about a decade - those things are tanks, and they vacuum really well too! I purchased a refurbished 15 year old unit for $175, and sold it once I built my current house, with zero carpet. Sold through Craig's list to a very wise couple, and they happily paid $150 for it.
Too soon to tell, but I recently found this website,
https://lastbrand.com/ I would love to own a quality tote than can handle my day to day requirements and not have the handles show signs of wear after 6 months, but wasn't quite ready to spend nearly $300 on Saddleback leather bag, so I'm hoping the $75 tote I have coming from Last Brand will last a few years at least! Saddleback is on my list of places to go - their company store is about 3 hours away, so I may stop in the next time I'm in the area.