About 6 months ago, a customer suggested a way to avoid this with Garmin Express. Here is the link to his thread:
">Old files in \ProgramData\Garmin\CoreService\Downloads">Old files in \ProgramData\Garmin\CoreService\Downloads
It is clear why one would want to keep these files; namely, to avoid a huge re-download of files. So, I wouldn't suggest Express automatically delete these files. But often the space on an SSD is limited; certainly, compared to the terabyte hard disks people have these days. People put the applications and data requiring very fast access on an SSD; fast access to critical data is why they pay a premium for those devices.
So a user doesn't have to research on the internet whether or not they can be deleted (assuming they can find them), it would be useful if Garmin offered a delete option with appropriate warning about potential for large downloads in the future. I suppose even a simple text message after the download alerting the user to the disk usage would work, but that seems too little to your paying customers. It was also suggested that the user be allowed to redirect the download to a different location, (probably off the SSD).