Thanks for the note. I can't think of any reason for such a limit unless there's some limit in the underlying XML format. If there isn't a reason for it, I'll clean this up in the next version.
For now, you may be able to circumvent the limit using careful wildcards (e.g. *.foo.com is two characters shorter than www.foo.com), etc. Otherwise, you could update Rules > Customize Rules > OnBeforeRequest to set the UI-HIDE flag on uninteresting sessions.
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