Generate map tiles, throw lots of queries at a local Overpass API, run custom large-scale analysis, develop a geocoding service, serve routing calculations... Many applications that public servers will let one query at sample scales, but for which serious use requires setting up one's own servers.

I'm mainly generating map tiles for offline use. I don't want to hit OSM official servers, this is too intensive (and they would probably block me).

Whatever they want. It's theirs.