I'm 38, for the record.
I think everyone who knows me knows I collect cards and other sports memorabilia, and I have absolutely no shame about it whatsoever. Do I think it is as "cool" as rock climbing or something? Well, no. But I can think of a million dumber ways to spend your time and money on things that people would consider "cool".
People who know me know I have an unusual obsession with the game of hockey, and understand that my collecting is just a natural extension of that.
Plus, I am around Grade 5 kids all day (I teach), so having a hobby that is considered a "kid's" hobby makes sense to people, I suppose.
I'm like newfiecomicguy...I don't do drugs, smoke or drink (much). This is my only really expensive passtime. My wife thinks my hobby is great, my kids think it is great, and even my dad, who thinks everything is a waste of money unless you can eat it or heat your house with it thinks it is a good escape for me. Teaching can be very stressful, as people know...and having something that brings me nothing but joy is important.
That is what it is all about...joy. It can't be about "the investment". One thing I have learned, if you love collecting, you are not likely making money in this hobby. Do I care? Not even a little bit. And I am not ashamed of it at all.