When I first started really getting interested in comics, I went about trying to read as many stories as I could that involved my favorite characters. At the time, reprints were generally limited to the best/most popular stories and, even then, they tended to get reprinted in a scattershot fashion. There were occasional reprint titles like Marvel's Greatest Comics Starring the Fantastic Four and Marvel Tales Starring Spider-Man plus DC usually filled most of their 80-page giants with old material. But if you were trying to track down a specific issue, it was often easier (and sometimes even cheaper!) to get the original rather than the reprint.
Part of the problem was that information in those pre-internet days was harder to come by. You might find a listing of Marvel Greatest Comics issues that were printed and you could count forward or back from an issue you actually had, but they didn't always print each and every issue, so there was no guarantees that issue #42 was in fact the one you wanted.
All of this led to something of a collector mentality. Even if you were more interested in the story that the actual first printing of the issue, you often had no choice but to track down and collect that specific issue in order to read the story.
I've always been very deliberate in my collection. I was more concerned getting books that served a specific purpose, rather than simply every issue of a title. That specific purpose might be getting as much information as I could in order to write an article about the Negative Zone or one about the events prior to Fantastic Four #1. What my collection essentially became was a large, ongoing research project with an ever-changing focus.
I've seen and heard repeatedly over the years about people trying to clear out the collection. In fact, I've picked up many comics for little more than the cost of postage from people who were simply thinning their libraries. While I certainly understand people that some people live in areas where living space is at a premium, I think some of those folks clearing out their long boxes don't really have that concern. So it seems strange to me to willingly relinquish a chunk of what could be used as future research. I know I went digging through my existing collection repeatedly while I was working on my book, and I came up with many fine examples that I ended up using that were only available precisely because I've never trimmed my collection.
I know that it would be much more efficient if I simply got digital copies of everything, but that's not entirely practical since so much of what I have isn't currently available digitally already. I'd have to scan every page myself.
But in any event, I want to make sure I keep as much of my research around as possible since I'm always coming up with new ideas and angles to think about surrounding comics. So I guess my solution for now is to just keep buying long boxes and book cases. (Although I could swear that I just bought bookcases a couple months ago; I really don't know how they're already full!)