The idea here would be to list directories for which file watching should be ignored and changes would only occur on a rescan interval (perhaps a separate rescan_interval setting).
As an example, I have several node projects in my 'code' share. Out of 298,470 files, 76,943 of them (~25%) change infrequently, but Resilio Sync is using 1.7GB of memory (I imagine most of that overhead is all of the file watches).
This above example is just one of many such paths that I would set to not watch, but to scan for changes periodically.