Well despite my short tenure on this board, I feel I have some applicable input for this discussion.
Some people just have psychologically addictive personalities. Some have it by way of entrepreneurship; others have it in the need to play video games all day every day; and some have it in collecting stamps, coins, poster, et al. In some individuals this proclivity wrecks lives, but in others it brings immense personal happiness. Some people are naturally good at, or naturally quick to develop, self-control and self-regulation. But those people are the minority. If they were the majority, so many men and women wouldn't go broke in casinos. Knowing your limits, and knowing when to stop separates a healthy addiction from an unhealthy one.
Here is a pleasant way of viewing all of the hours lost, and money spent, in a hobby --- "What else would you have done? Where else would you have spent it?" Any money you lost wasn't truly a loss... It was a purchase of entertainment. When I purchase a 300page book for $20, what am I buying? Answer: The ~10hours it will take me to read it, the knowledge it gives me, the feeling of accomplishment when I finish, opening new pathways of thought, something to discuss with others, and a new mantle piece. I think you can use the same logic to posters. Even though in the long run, you may have sank too much perceived time and money, what you really did was *buy* an incredible amount of entertainment, purpose, and belonging.
You can only become knowledgeable in a field by sinking a tremendous amount of hours into it. And that knowledge isn't worthless. Would you really be any better off if you had, instead, spent 12 hours watching football every week like most Americans? Not that football is bad, or good. It's merely entertainment. But so is poster-collecting.