Do I need to retain all .ics files to retain my Calendar entries on my MacBook Pro?

I've accumulated a ton of old .ics files. After opening each .ics file and ensuring the calendar entry is made, do I need to retain that .ics file? Are the .ics files used only to input the appointment info into iCal or are they required to make sure the appointment "sticks" in the iCal calendar? I have a ton of old .ics files that are taking up space, but I've never trashed any because I didn't want to lose the iCal entries. Please advise, and thanks in advance.