So, I will pass on what I have discussed with my brother-in-law who is an Electrical Engineer that writes software to test flash memory:
1. Flash memory is built with additional fail over storage (so a 1GB SD card actually has a certain % more memory than 1GB).
When a section of memory fails it is marked bad by the flash controller and some of the fail over memory comes into service (marked bad much like failures on standard hard drives... although I get the impression the flash controller may be the thing remembering it's bad... wasn't clear on this now I have something else to ask him)
2. Flash memory will fail... it can only be written to so many times before it will no longer be able to be written to... and the number of times is definitely not as high as a standard hard drive
So it's likely that you can extend the life of a flash device by writing to it less often.
And, not from my brother-in-law discussions, I personally had a flash drive fail (I was using it as the master copy of documents as I moved data between my work machine and home machine while working toward an online degree). When it failed there was no warning previously. It simply stopped working... wouldn't be read and wouldn't write. I suspect my batch file that performed the backups to it must have written to it too many times (it was a smaller 128MB drive so, considering the above discussion about fail-over memory a smaller drive SHOULD fail faster...)
Hope that helps
IF I HAD A MINE SHAFT, I don't think I would just abandon it. There's got to be a better way. -- Jack Handley, The New Mexican, 1988.