I have some favorites, many which have been hand me downs from my mom, who got them years ago:
1. Kitchen Aid stand mixer. I think my mom got this in the early 1980s...it is still pretty much perfect. All of the attachments work, you can grind dried fruit/nuts/meat or whatever in the grinder, I whip perfect whipped cream up, countless batches of cookies, etc. Every now and then it has a moment where it seems like it might be struggling (usually when I overload it with a triple batch of cookies), but then it just pulls through! I hope I have it forever! Meanwhile, my mom has a newer version and totally regrets gifting her old one to me, because it works so much better!
2. Champion Juicer. Man, I don't even know how old this is (late 1970s??), but I grew up with my mom using it basically daily, and then when I moved away as an adult she gifted it to me. I don't use it nearly as much as I should, but it works perfectly and makes the best juice ever. It also makes amazing dairy free ice cream out of frozen fruits!
3. Whatever old cast iron pan I've had since college that I found at the thrift store for $1.00. It seems way nicer than the Lodge one that I found a few years later, and has a beautiful sheen to the surface that seems to indicate many years of use. I never use any butter/oil in it and nothing sticks. I use it every day and hope I never have to buy another one!
4. Used Patagonia clothing. I occasionally buy new things from them, but notice there is a distinct difference in quality from about 10 years ago and back, vs. now. So any time I find an item of clothing at the consignment shop that is older (you can honestly tell just from thickness of fabric/stitching) I pick it up. I have a few beautiful dresses that I can't imagine ever wearing out, the fabric is amazingly thick and soft. A couple of jackets I have found here and there are just amazing. I do have one newer hardshell jacket I purchased that seems to be high quality, so I hope it will last a lifetime as well.
5. LL Bean wool blanket. I don't know how old this is, my dad has had it since college. It's scratchy, and wool-ey, but amazingly warm if you really need it. I keep it in my car as an emergency during winter (live in the mountains), and use it as an extra layer on especially cold nights. It's great for picnic-ing, camping, moving furniture, everything...it has seen a ton, and doesn't even have a loose thread.
ok so most of mine are amazing things my parents handed down to me. But, maybe that's the point, they are so high quality that they can actually be passed down...I don't know if I own anything that I've actually purchased new now that I can imagine holding up to be passed down. Everything I buy new seems to wear out within a few years of use (although I am admittedly hard on gear/clothing)
I do own a Vitamix (also handed down from my mom) and I think it's about 8-10 years old. I don't consider it a BIFL item though, because I can tell it is getting worn over time. It is still just as powerful, but complains loudly at things that it used to blend with ease. I fear an implosion in the next 2-3 years, and probably won't replace it