Small Applescript to automate thinning your local Time Machine snapshots.
The script can be scheduled to run periodically as a Calendar event (follow the instructions on the link https://smallbusiness.chron.com/schedule-automator-tasks-mac-os-x-39132.html) or with a plist via launchd.
To schedule the script with a plist first edit the plist file and make sure you replace USERNAME with yours in place in the plist file. The plist is scheduled to run the script every 3 hours (10800 s) and assumes that the repository folder lies on your Desktop, therefore modify the time and repository path accordingly if needed. Lastly, open a terminal and execute the following commands in order to copy the plist file to LaunchAgents folder and then load it.
Create the LaunchAgents folder if it doesn't exist:
mkdir -p ~/Library/LaunchAgents
Copy the plist file to LaunchAgents folder:
cp -p thinLocalSnapshots.plist ~/Library/LaunchAgents/
Load the plist file:
load -w ~/Library/LaunchAgents/thinLocalSnapshots.plist
Happy thinning!