Gizmo -
Do you mean less than 10,000 files in a given directory? I've had mail queue directories that get over 300,000 files in them and they only seem to crawl when they get up over 100,000 files in them. The directory structures seem fine with 80,000 files. Have you seen issues with directories that have only 10,000 files in them? To me that's a fairly small number of files ...?
