Alex,
I imagine that some folks are wired in such a way that they fall into the trap of near-obsession when they develop a new habit (hobby in this case). I'm looking in a mirror as I type this. If that is you, I suggest that you stop collecting at this stage in your life. It's too easy to "check out a web page for a minute" and have that minute turn into an hour or two. Your eductation and/or career development, not to mention your personal and relationship development is of course hugely more important than your collection.
If you do have that obsessive personality and you still want to collect, maybe you can focus your obsession on meeting a very very strict budget and time constraint (only work on your collection between 6 am and 8 am on saturday and sunday mornings for example). Make your obsessive goal the time and budget constraints. I've been succesful at this in spurts, but I can tell you that is treading on thin ice.
Pretty much what Zach Wheat wrote a few hours ago, but I know from experience that his model is much easier said than done for some people. I've been trying to master doing things in moderation for over 40 years now
Good Luck,
Tony