Does Google use document inception date for ranking new internal links?

No, Google doesn't use the original document inception date to discount the value of new internal links. If you add new internal links to an old page, Google just sees the updated content and will recrawl and process those new links normally. In practice, fresh internal links from updated pages can absolutely help rankings as Google sees the new link graph after crawling. You can see this happen in server logs and with Search Console's 'Links' report where new internal links show up after a recrawl. Just make sure those pages actually get crawled again soon by updating XML sitemaps or internal navigation if needed.

No, Google doesn't just use the original document inception date when re-evaluating new internal links you add later. Any time you update an old roofing page and add new internal links, Google crawls it again and treats those links as part of the current content, not locked to the old publication date. I've had roofing clients update their old blog posts or service pages with fresh internal links to high-priority service areas, and rankings did improve within a few weeks in some cases. Make sure your sitemaps update, ping Search Console, and add links where they make sense contextually, not just dumping them into footers. From what I've seen, Google rewards fresh internal linking if the content quality stays up and the links are actually relevant. Don't stress about the original doc date unless you have structured data or visible dates showing up in SERPs, that's a different thing.