google will not follow links on a page unless it has a pr of 4 or more - so unless the page your sitemap is on has a pr of 4+ then it'll not make any difference anyway, apparently. i find it is more important to get google to rank your site rather than getting it to crawl it.
ps - there are some useful php tools out there which will build you a sitemap based on a directory structure, so you don't have to keep re-building one.