ecnext - 9:17 pm on Apr 29, 2010 (gmt 0)
I'm assuming those 70,000 URLs are not all the same type of page, like a product page for example. If that's the case, consider breaking up the list of URLs into logical groups and submitting them in separate files.
This can help in tracking sitemap indexing stats, as well as make it easier to adjust the other options such as changefreq, last modified etc.
You may also want to read this Google paper which also gives examples of how CNN and Amazon structure their sitemaps: "Sitemaps: Above and Beyond the Crawl of Duty" [www2009.eprints.org...]