Powershell script for zipping up old files
I spent several weeks writing and tuning a script that moves old files to a timestamped Zip file. Here are a few guidelines I learned that may help:  

1) Move variables into script parameters so they can be changed at runtime without editing the file: 

Param($File_Path = "C:\Users\Administrator\Downloads\Testing\*", #File path of file to be cleaned    
  $Send_To = "C:\Users\Administrator\Documents\ARCHIVE2", #Location of ZIP file
  $Old_Files = "C:\Users\Administrator\Documents\OLD_FILES", #Location of old files before being zipped
  $Days = "-65"
)


2) Filter usually means 'criteria for filtering a list'.  Calling the list of files $Filter is misleading. $FilesToZip might be a better variable name. 

3) There are lots of reasons a file can't be moved or zipped (in use, doesn't exist, no read/write permission, etc.) You should have a try-catch block around Compress-Archive to account for this, and fail or proceed gracefully. Using ZipFileExtensions, an error created an unusable file until it was finalized. Compress-Archive may be more robust, but there are still chances for failure (try pulling your network cable while creating a large archive of files on your LAN). 

4) There's no need for an intermediate folder, and it creates more opportunities for failure. You can just compress the file into the zip and delete on success. 

5) The message 'No old files found' is misleading. Reading it, I would think that there were no files found matching the age criteria, when it really means the intermediate folder doesn't exist. 

6) Don't you need a .Zip file name for the -DestinationPath? 

7) Write-Output is usually used for return values rather than messages. Write-verbose, or Write-Host are more appropriate for status messages.