After regular use
Remove obvious sweat and grime before it builds up. Frequently used tack generally needs attention more often.
After wet or dirty conditions
Mud, heavy sweat and wet conditions can justify cleaning sooner.
Inspect while you clean
Routine cleaning is also a useful time to notice wear or stitching issues.
Keep the routine simple
Clean the leather, allow it to dry, then condition as appropriate for the tack and its manufacturer’s instructions.