1. Always make new extracts from the updated planet file using `osmconvert`
2. Update the planet and keep temp files (`osmupdate --keep-tempfiles`). Apply `osmupdate [-b | -B] --keep-tempfiles` on extract files. This reuses the downloaded diffs.
2. Update the planet and keep temp files (`osmupdate --keep-tempfiles`). Apply `osmupdate [-b | -B] --keep-tempfiles` on extract files. This reuses the downloaded diffs and therefore saves time (for downloading) and bandwidth.
3. Use `osmupdate planet.pbf diff.o5c` to generate a diff between old and current planet. Apply the .o5c file to the extracts (is this possible?) and to the planet to update these files. The .o5c file should also be usable to update databases with osmosis/osm2pgsql according to http://wiki.openstreetmap.org/wiki/Osmupdate#Assembling_an_OSM_Change_file .
