I’ve faced the same issue; manually converting multiple ICS files is messy and risks losing recurring events or details. From my experience, SysTools ICS Converter is a solid choice for bulk conversion.

Why does it work well?

List item supports batch processing, add multiple ICS files or an entire folder at once.
Converts to PST, CSV, iCal/ICS, and other formats.
Preserves event details, including descriptions, attendees, and recurring events.
Can handle large ICS batches without errors.

Tips:
Always back up your original ICS files before conversion.
After conversion, spot-check a few events to ensure recurring events and reminders are intact.
If using CSV, check that all columns (start/end, description, attendees, etc.) are correct.
Overall, it’s a reliable way to quickly convert multiple ICS files without data loss, saving a ton of time compared to manual methods.

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