I think the best advice I ever read on collecting for investment purposes is to make sure you collect the things you love. That way they will always be valuable to you. Maybe not so much to others, but you will still be happy.
I have a friend that has collected CASE knives as displays only for some time. If he could sell his collection for anything close to what he has in it, he would. But he has found collectors of CASE knives to be picky, and when the overall economy is not so good, neither is the value of his collection. Apparently there are plenty of Johnny Cash, Dale Earnhart, John Deere, and dead presidents on knives out there.
I would think collecting GECs would be even more tricky. Yes, everyone here knows them and respects them. But on the other hand, if this forum shut down, where would you sell your GECs? I am in the middle of a knife culture and no one I know has a knife from the GEC group or its sisters, nor have they ever heard of them. Unless you found that one person that just had to have a certain pattern with a certain set of covers, you might be hanging onto your collection for a while.
Also, think about this. A friend of mine bought a really nice COLT .45 auto back in '72 for $125. Light use, excellent care, shoots like a dream. He was going to sell it and thought he had made a killing on the pistol as he was going to get about $650 for the gun, including a Bianchi holster he paid about $75 for back then. Yup, he was real excited until another friend of ours in the financial business pointed out the cost of other things back then. After running the numbers, his "investment" didn't even keep up with inflation. That was after all, 40 years ago.
Couldn't sell it locally after about 6-8 months of trying. The variant he bought was cutting edge at the time, but no one cares now. Other guns have come out that are more popular now, and even though .45 autos are quite popular, his isn't.
Now he wishes he had just shot the dickens out of that gun when ammo was affordable. Now he has a nice gun he can't sell, and due to ammo prices (again) he has a gun he can't afford to shoot.
I like the advice you got above in earlier posts. Invest in your GECs to use as tools, ones that will probably outlast you. Buy 'em, use 'em, and enjoy 'em.
Robert