I found that it was the law of diminishing returns.
I was 'Hiding' and 'Showing' lots of entities depending on visibility, but after the number of entities rose over 80 (yes I did need them all) it made almost no difference.
I was 'Hiding' and 'Showing' lots of entities depending on visibility, but after the number of entities rose over 80 (yes I did need them all) it made almost no difference.