The current size of the store files is just over 6MB. Given current disk sizes, reducing it to half (or less) doesn't really move the needle.
Also, given that we store the updates in memory in RAW form, using the same amount of space on-disk is a non-issue.

+nparker@, shess@: Please feel free to re-open if you disagree.

I agree with this, but something to keep in mind is update I/O costs, especially for low-end devices which may have inadequate flash controllers.  Even there, though, I think the better wins are in strategies which use log files to collect incremental changes with periodic compaction, which can plausibly cut I/O by an amortized order of magnitude.