I have been using SD cards for a long while and have had little trouble (except for one card where the connectors peeled off the card in the camera, damaging the reader, I don’t use the cheap brands anymore), I have misplaced a few cards and deliberately dissected an old one. They have all given me good service and I have migrated to using the fastest ones I mainly still use 4Gb & 8Gb (giga bytes) in size (that's plenty of shots). I generally use Picasa to unload the cards on a computer and I have always been happy to let Picasa delete the photos off the card (it does seem to do some form of verification after loading the files before it deletes anything from the card.) I have used lightroom (way too slow for me) and photo mechanic a few times with similar settings, and no problemsOne of my fastest cards has started to “forget” to deleted the previous uploaded photos. Which is not a real problems in picasa I just make sure I have the exclude duplicates button checked. Anything I have already loaded show up with a red cross on a white circle. So I have my little 1-2-3 checklist for any picasa import. 1. Excluded Duplicated, 2 – Delete only copied photos 3 – Import all. Works fine and it is now just a habit.
The majority of on-line sites and experts seem to recommend that you never clear your card till after you are sure the files are uploaded and safely backed up to a second place. Seemed overkill to me because as long as you have not taken new photographs you can usually recover deleted files from your card with suitable recovery tools. You should always review what you have just uploaded, and that will highlight if anything is missing. I know some people have months worth of photos on large capacity cards, which could make it hard to spot missing images. I prefer to off-load my cards as soon a practical (ie each day, or session).
The pesky little undelete was easily solved by deleting the files on my card on the camera before any new sessions. On my Pentax I just need to press the delete button twice, and then Ok to confirm when looking at any image, to delete all the photos on the card. On the Canon its a bit more complex because you have to delete the pictures individually, so there I have chosen to reformat the card. All easy enough. Then I discover on two occasions that the card was locked, the little plastic tab has moved down. That was the cause of the “forgotten” to delete issues the card was being pushed down a little as I inserted it in the card reader. So I have retired that card from active service.
This weeks digital story podcast, has an interesting segment on how digital memory cards work and it reminded me of this. Derrick’s suggestion is to reformat the card to suit the camera and I had actually noticed that I felt my Canon was getting a little sluggish in burst mode but after I had reformatted the card it did appear faster, So I think his advice is good. If you swap cameras it may pay you to reformat the card so the directory structure suits it.
So my suggestion here is not to slavishly follow my workflow or anyone else’s, but figure out what is safe and works for you, and make it a habit to follow those steps, not a chore.