Even if someone makes 300+ reports, do all the reports stay in the history, starting from the first report, or are only the reports mentioned in the history starting from the 301st?
To see your report history, you need to have at least 300
good reports, not 300 reports.
Do these reports have a visibility decay time, or are the details of every report made visible, even after years?
Your report histroy (if available) displays your reports in the past 30 days.
I see; while reading the thread, I saw some users mention 300+ posts (Good was not mentioned), so I assumed it's just 300+ (Inc. good, bad, and unhandled); I guess everyone makes mistakes.
If just 300+ were the case, then any newbie and brand new account would be getting that optioned enabled for them, just by spam reporting any posts (I guess this was taken into consideration)
This is off-topic (Can be avoided to answer): Are there any rule against bad reports?, It's encouraged that users should report posts that are spam, off-topic, or irrelevant, but what stops a mass farm of users from mass reporting any posts coming their way.