There should be a way to check for all the blocks that you have uploaded to the system, weeks or months later.
The check should be quick, searching for blocks but not downloading them. And if any blocks are missing there should be a option to upload them again (if the user has them of course).
This will prevent files from becoming partials, having one or more missing blocks on the system.
An indicator should be provided for how many nodes seem to be holding each block so the uploader can get an idea of how wide spread his blocks have been distributed.
It may be possible for something like this to happen slowly in the background on some of the files searched so that instead of pushing a random block out, a priority could be put on pushing blocks that may start to get scarce.