Hi Amy -
6000 is the limit to save our database - if 250,000 people are executing an infinite search at the same time, the planet will explode
However, you can search older cards of course, but you will have to narrow your search to see more or older cards.
So for example, a search for "Christmas" will show you 6,000 very recent cards.
But searches for specific stamp sets, techniques, etc. will give you more longevity in the search and more specific results.
Make sense?