@lezboyd: YES, the amount of links is the NUMBER 1 impact on memory usage. Can you provide a screenshot of your about dialog of JDownloader, see
https://support.jdownloader.org/Know...tion-directory
It highly depends on what type of links those are as depending on site links require more/less memory.
Please also see
https://support.jdownloader.org/Know...vmoptions-file
You can modify vmoption file to allow larger heap memory to Java and thus more links are possible in JDownloader and better GUI experience you will have with many links.