30 minute TileMill exports can be on the fast side depending on the size/type of project, but in your case there's probably ways to optimize this much further.
The most important factor is to make sure your data is properly indexed:
- For Shapefiles, use the
shapeindex
command-line utility. (On Ubuntu this is provided by themapnik-utils
package. I'm not sure about other platforms but it may be included with TileMill already.) - For PostGIS tables, make sure there is an index on the geometry column with the
USING gist
option. - SQLite files will be automatically indexed by TileMill.
- GeoJSON files cannot be indexed and should be converted to another format for best performance.
Having everything already projected to Web Mercator (EPSG:3857
) is a good idea too. TileMill is also reasonably well-optimized for EPSG:4326
.
Finally you may want to tweak your buffer and metatile settings, however for a smaller project like this it may not make much difference. If you are only exporting points (without labels) your buffer only needs to be as wide as your largest marker-width (the default buffer-size is 128 pixels). See this guide for more information about when and how to adjust buffers and metatiles.