I think the only time I've ever intentionally bought multiple copies was with X-Factor #1 thinking it would be as popular as the relaunch of the X-men and that was only 3 copies. It wasn't the worst idea @ $1.25 an issue. Most of my other duplicates are from various sources such as upgrades, freebies from purchases here, forgetting I already had that issue , or drunken eBaying . I did acquire a collection back in the mid 90's that there was some cross-over with my collection but that included some key issues like ASM #300, New Mutants #98 and all the different covers of Spider-man (McFarlane series) and a bunch of early Spawn issues.