Microsoft has packed it in with mobile and Windows 10. As of December 10, 2019, Windows 10 Mobile users are no longer eligible to receive new security updates, non-security hotfixes, free assisted support options, or online technical content updates from Microsoft for free.
The Lumia 640 and Lumia 640 XL shipped with Windows Phone 8.1 Update 2 (through the Lumia Denim software package), and both phones are upgradable to Windows 10 Mobile. Initially in America, the Lumia 640 and 640 XL were offered with a free one-year subscription to Microsoft Office 365.
End of support means there will be no more product or security updates for the Windows 10 Mobile operating system (OS).
Microsoft has no current plans to remove historical Windows 10 Mobile updates from Windows Update.
The Lumia 640 is now 5 years old and the limited internal storage is as much of a problem as anything. Today however, mobile devices with 64GB or more are very common.