SiteMaps - Google is Dropping Site Map Pages!

Pages not caching in Google

[Whitey]

We have three sites with varied content, page structures and no's . All have a sitemap linked from the front page.

A & B were also submitted through Google SiteMaps.

Site A - submitted first around 4 months ago - 2 pages cached
Site B - submitted second around 2 months ago - all cached
Site C - nil cached [ not submitted thru Sitemaps yet ]

Needless to say there are huge variances in the total pages indexed. These sites are caching differently and A is slow.

Is Google dropping sitemap pages [ ie www.yourdomain/sitemap/ ] from the index? Surely Google can't be treating these as pages to be dropped from the index in consistancy with it's claim of BD working properly.

Can anyone comment if there sitemap pages are fully indexed?