I'll add my story and advice/warning.
I'm 27 and I have lots of lego's from my childhood late 80's early 90's.
When i finally went home to ge tthem, I had a bunch of sets asembled in my parents basement and the dust was so thick and nasty, you couldn't blow it off or even wipe it off.
I actually took all my sets apart, piece by piece, and cleaned them with a rag and bucket of water and a towel to dry them. It took me weeks, literally. I'll never leave a set assembled and not dust it for more than a month.
A little bit of canned air goes a long way. As long as you dust them off or blow them off every now and then, they will be fine, and in perfect display condition.