Had a Longhunter that old and now have 26" Hunter and 22" Tactical. All bullet proof, comfort good, biggest difference is the harness, belt, and Lumbar. An improvement but the old one would still serve today.
I have one of the older original duplex frames. I actually really like it. I have arrow stays in mine, and to me, it makes for a very comfortable, lightweight, hauler. I primarily use my markhor bag on that frame. With the smaller lumbar pad, smaller shoulder straps, and arrow stays- it is remarkably similar to a Stone Glacier Krux frame.
I also have a tactical frame I use with a cargo panel set up for reference. To be honest- I think the original frame is more comfortable.
I have an older duplex and prefer the newer standard(Tactical) duplex. I like the ungraded lumbar pad and the way the new power pulls lock up. I prefer the duplex over all other frames because it has zero flex with a load on. Durability wise I don't think there is much difference.