I would say that's true for any property being published by a company that's still in business or whose rights are owned by a big company. But a lot of that copper self-published drek I can't see a demand for at any price, at any time.
If the drek had a good run in the 80s, its probaby smartes to invest in now.
http://www.ebay.com/itm/THE-FISH-POLICE-VOL-1-1-UNREAD-1985-FISHWRAP-PRESENTS-HAIRBALLS-NM-/400925870757?pt=LH_DefaultDomain_0&hash=item5d590b4aa5&nma=true&si=cCTwDudGe%252B4b5k1cNGahWuAER9I%253D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557
http://www.ebay.com/itm/JUSTICE-MACHINE-ANNUAL-UNREAD-VOL-1-1-1983-1-st-appearance-of-Elements-Fn-/400925858845?pt=LH_DefaultDomain_0&hash=item5d590b1c1d
When a friend of mine moved coasts years ago, he left his comic collection with me. I keep thinking I'm going to get around to packing it up and sending it to him. I mentioned it to him recently, and he basically said do what you want with it. You can sell it and split the money with me. Looking through it today, there's a ton of '80s indies. Some Critters, some Usagi Yojimbo, a couple copies of Animal Man #1. Oh, and a Detective 411.
I just recently bought a collection with complete sets of American Flagg, Concrete, Animal Man, '87 Justice League etc.. I was so psyched I didnt even notice there was a mid grade Jimmy Olsen 134 in there. Yup, my basement has very little room left now