There’s not really any functional limit, but there are some practical limitations.
Are you planning to put all of these calendars into a single shared shortcode? I would not recommend that unless each one only has a few events per month —?the display will blow out beyond usability if there are a lot of events.
The other matter is performance… the parser has to load all of those calendars and put their data into a single PHP array for output on the page. Your server may run up against memory and processing timeout limits with that much data.
If you’re planning to put these into separate calendar shortcodes (i.e. on different pages), then it shouldn’t be a problem at all. A site could have thousands of pages with a different calendar on each one and it should be just fine.