So true. A lifelong "collector" here starting with pennies, baseball cards and Matchbox cars in the 70's. For the 80's I collected books. 90's was comics and 2000's was computers. 99% of it all is now worth less and worthless. For the few items worth more, the appreciation is from 10% to 100% over 40 years.
But, it was always fun seeking out missing items from a series and hoping one day years into the future I'd posses a truly rare item. A bit like playing the lottery, I suppose, with similar results.
Good luck on discovering a hidden gem in your boxes of stamps! It's the wonder of 'what if..." that's rewarding all in it's own.
RE: Perspective: How Turning Hobbies into "Investments" Often Destroys Them!