Well, if one set is before the 90s and one set is after the 90s then there is nothing in the 90s to be considered?
I still use my Technics SL1200mkII, some Carver amps (2 M500t's and 1 M500), a Carver preamp (C-1); those are all from the 80s. I had a nice Fisher receiver my dad got sometime in the 60s and I used that into the early 80s before drinks got spilled on it during a party. I think all that stuff was very well built with quality components and could be expected to last quite a while.
The components I've purchased in the 90s and since I don't think are as well built for the long run; a Pioneer receiver (VSX505) ran I think somewhere around 10 years before developing an annoying buzz, a Pioneer 919 I bought a few years ago crapped out a little after 2 years (think HDMI board issues, some analog stuff still works). I bought a Samsung Blu-Ray BDD6100 that developed issues on blu-ray discs after several months (plays dvds fine tho). The first flat panel I bought, a UN60C6300, had excessive flashlighting/clouding and had to be returned, but the PN59D8000 I replaced it with has been fine so far despite too others having a variety of issues. First iPod I had crapped out in a few months as did an early Sansa player. Had a DirecTV dvr (HR21?) crap out in two years. Several laptop computers with broken ac power/board junctions and one with hinge electronics poop out. Current manufacturing, transportation and pricepoint issues all conspire against well built and maintainable a/v gear in general, though; it's disposable now.