Buy an extra SD card for Your trail cameras so You can swap out the card that's in the camera out in the field,always pack an extra set of batteries in case you need to swap them out also.When I get a large amount of pictures built up on a card I delete the ones with poor pic quality or of Animals I don't care to save then I usually have the rest of them put to a CD/DVD disc for viewing references later on.

Try keeping the same SD cards with the same type/brand of trail camera.Im up to around 6-7 different trail cameras....it can get confusing sometimes?