Yeah, I also keep on asking myself the same question and I fear I know the answer, not sure though.
My first collection were keyholders. That was in my youth, I got them all for free or as gifts, just put them in a box. Them came Swatches. I made the mistake of buying them too quick, so I now have 70 Swatches from 93-95, lousy collection. Then I collected 1:43 Formula 1 models and I have about 40 cars, mostly from 95-97, lousy as well. Last was wine, I can't even tell you how many bottles I have and currently I don't drink anymore. In between was a Playstation wit accessoires and games, 1:18 car models, Whisky and things I don't remember now.
All my collections have in common that they lasted 2 to 5 years and that I bouht way to much in a short time. Obsessive-compulsiness? Everything I start quickly runs out of normal quantities and my accounts suffer big time as I don't really think about how much I spend anymore. I know that I get addicted quickly to everything I start, I'm a junkie...
As for the lights, my love for them started with the Mags 20 years ago, my first LEDs 2 years ago and the real collection 1 year ago, the madness 2 months ago and I wonder how it will move on, it just can't the way it goes on currently. Holy sh**, the lights don't spare me the psy, they are about to send me to the psy!!! I need another titanium light!!!