Oh dear, sounds like you are experiencing some trouble with your memory cards?
In short, from what I know, I don’t think there’s any real way to tell when one is getting old. I’ve heard 5 years is a typical reliable lifespan of a CF card. But I’ve also heard that they can last a lifetime. (But perhaps those are for the super expensive ones that have lifetime warranties. LOL)
I’ve had very positive experiences with my CF cards, and I have always used SanDisk. I don’t buy the cheapest on the market, but I also don’t buy the most expensive. So the cards I have I expect to last a while, but do not expect them to last forever. I’ve been using my CF cards for anywhere from 2 to 9 years … and the surest way I’ve lost pictures is by actually loosing the card. 🙂 I was using someone else’s Kingston one time and it corrupted on me, so I told myself I would never buy Kingston after that.
As for recovery, I have had to recover pictures before. I have a friend who owns some software that recovers deleted pictures, so let me see if I can get in touch with him and ask what software he uses. The important thing is to not use the card that has had the pictures deleted off of it! Will get back with you on this….