Hey Sunvista!
Not sure if you are tied into Hobie Fleet 32 in Va Beach, but if you aren't...check their website at
http://www.hobiefleet32.org. That fleet has a good mix of old and new boats and are some great folks to sail with.
Like anything, stress, usage and age takes its toll on boats. But has J_Eaton said, the 80's boats seem to be built like tanks. If the boat has been well cared for, it really will sail a very long time. However, if it has been left uncovered on the beach, exposed to the elements, allowing some corosion to set in, that time will shorten.
Stories you hear about boats folding like accordians are usually due to a delamination issue, something you can continuously test for simply by knocking on the hull. Without being overly scientific, it seems that several things help promote delamination
1. exposure to elements
2. Moisture inside hulls (and they aren't dried out)
3. Improperly installed deck ports (exposing laminate to elements)
I recently sold an 84 that is still hard as a rock and I have sailed it in very demanding conditions down at Va Beach (the Version 2.x regattas). Its also been raced hard for years (by 2 prior owners to me) and the guy I sold it to will continue racing it.
As for other noises, you sometimes seem to hear more creaking in new boats than on older ones, probably because the newer ones haven't worn a bit. I would imagine that you may also be hearing the foam bouncing around in the hulls. One thing I would check is to make sure that the stress of waves hasn't knocked loose the shoes that hold the pylons to the hull. If you see a bulge through the side of the boat, that could be a possible symptom. I believe there are posts on here about fixing that, but it does require installing pot holes to access the shoe.
Take care of the boat and my guess is that it will take care of you! BTW...smart call on replacing the standing rigging. Dismasting in the Atlantic isn't that much fun.
Cya!