To enable ast-mod for "not parsed" URLs or not?

[mailaski]

Hi,
In the settings I see that you can enable last-mod for "not parsed" URLs but additional HTTP HEAD requests are required in this case.

Enabling is a courtesy to search engine spiders, but is it usefull for SEO or does it only has a marginal impact?

What is your experience on this?

[XML-Sitemaps Support]

Hello,

this option is only useful if you have custom setting for "Do not parse" option (otherwise all URLs are parsed anyway).
Also, it doesn't affect xml sitemap, but only allows to have page titles displayed for "not parsed" pages in *HTML sitemap*.