Extending the default restoration time period in SharePoint Online more than 14 days

I think that 14 days could be misleading, though I can see it mentioned in the https://technet.microsoft.com/library/jj819267.aspx#Data backup:

"Data protection services are provided to prevent the loss of SharePoint Online data. Backups are performed every 12 hours and retained for 14 days. This describes the data backup services as offered when SharePoint Online is generally available."

Restorations can only be completed for site collections or sub-sites, not for specific files, lists, or libraries. If you need to recover a specific item, find it in the Recycle Bin, right-click it, and choose Restore.

This is more when a site collection has been damaged beyond repair and needs a complete restore I believe.

Elsewhere, in https://support.office.com/en-gb/article/Restore-a-deleted-site-collection-91c18651-c017-47d1-9c27-3a22f325d6f1, for when a site collection is deleted:

"The Recycle Bin in SharePoint Online in Office 365 for business provides a safety net when an entire site collection is deleted. When a SharePoint Online administrator deletes a site collection, it is placed in the Recycle Bin, where it is kept for 90 days before it is automatically permanently deleted."

For items that are deleted it says in https://support.office.com/en-gb/article/Restore-deleted-items-from-the-site-collection-recycle-bin-5fa924ee-16d7-487b-9a0a-021b9062d14b#ID0EAAIAAA=Online: 

"When you delete content from a SharePoint site, it’s sent to the site's Recycle Bin or first-stage Recycle Bin, where you can restore the deleted content if needed."

"In SharePoint Online, the default retention time is 93 days for both site recycle bin (first stage) and site collection recycle bin (second stage)."

"The site collection recycle bin retention starts at the same time for both recycle bins when the item is first deleted, so the total maximum retention time is 93 days for both recycle bins."

These recycle bins don't stack and offer at most 93-day retention that is discussed here as well in this discussion - Recycle Bin Duration.