https://bugs.mojang.com/browse/MC-100524
Log files were previously overwritten when more than 7 were created on the same day. This is caused by Log4J's default behavior with DefaultRolloverStrategy, which defaults to a max of 7.
While a max of 1000 doesn't fully stop this problem from happening, for 1000 log files in a single day to be reached the server would have to restart faster than once every 1.5 minutes, which is unlikely to happen. So 1000 seems like a good limit. A higher max isn't used because when it gets higher, there are performance hits due to the way Log4J checks for the next file.
Something the log4j ConsoleAppender does makes the console work correctly
on Windows. After trying to pull pieces of it out and run them manually
I decided to just put the appender back. We now once again start with the
ConsoleAppender then remove it immediately after starting.