[conor912]

I would venture to guess that no one starts a set with eventually selling it in mind, though decades are a long time to keep something and not get bored with it (insert wife joke here).

Art collectors are often grooming and reshaping their collections to keep them fresh and interesting. I look at cards the same way. I think a lot of collectors would agree that the only thing I will never sell is stuff from their childhood and/or of sentimental value. The great majority of my sets (sets make up 90% of my collection) are for sale for the right price, as building them is a lot more fun than owning them once their done, IMO.