Reinsert on Demand
Because of Freenet's poor data persistence, many users and a few applications (e.g. Frost) insert a file (or just generate its CHK without inserting it), and then reinsert it whenever anyone asks for it.
Obviously the latency involved is significant, but not as large (usually) as fetching weeks old data - and if it's much more than that it may not be fetchable at all, unless it is small and very popular.
The problem is that reinserting the same file to the same key - or inserting predictable content in general - makes certain attacks much easier, notably the mobile attacker source search attack.
Random reinserts might be an option.
Selective reinserts where you know what blocks are missing are also possible.
We should also support reinserts better in general: If any user who has a file can reinsert it easily, including the top block (via binary blobs), then hopefully the reinserting person will be a low value target, not the original content author.
There are also possibilities for keeping content available in a distributed manner via some sort of probe requests and then reinserting.