Let me try to provide some more details. You only have easy access to 7 un-owned cards at a time. Those are the previews. Both the cards you own and previews of cards you don't own are stored in the models folder and data folder on your computer. The models folder has one folder for each card and that folder stores both demo files (previews) and vghd files (encoded clips only you can play). The data folder contains one folder for each card that contains control information and images needed by the iStripper application. The data folder also contains additional control files.

In the models folder, the folders for the cards you own are much larger than the folders for cards you don't own. A folder for a card you own will contain 20-30 clip files while a folder for a card you don't own will contain just 2 or 3 .demo files. It is possible and quite likely that you have dozens of folders for cards you don't own. When a card rolls off the preview tab on the UI, its data is not normally erased. Every card on your hard drive is recorded in the models.lst file in the data folder. This binary file has flags that indicate whether you own the card and if it is currently in your previews tab.

So, if you select a card to add to previews and that card is already on your hard disk it is just a matter of setting a flag. If you don't have the demo files on your hard disk, they must be downloaded which can take a few minutes. This means that while you only have easy access to 7 previews at a time, you can quickly swap in cards that have previously been on your previews tab. It is possible to have all the preview data for hundreds of different cards on your hard drive, but each card takes up some space.

To learn more, you need to do some experimenting. Try making a playlist with, say 4 cards you don't own. Play that playlist while those cards are still on the preview tab. See what happens. Then wait util those cards are no longer on the preview tab and try playing that playlist again. See what happens.