DCU future beyond the 30th Century.

Ok DC experts. I wanted to know about the futures explored beyond the 30th century (which has become a mess) and see what other eras has been explored by the present time characters.

I'm asking for the eras beyond the 21st-31st time, which has been explored several times.
The most obvious time are the Century 853th with the Justice Legion, but I also remember than Flash has explored the century 64th and Green Lantern has explored the 58th century.
Which other eras has been seen more often?

1 million years from now, is what I would like to see explored;)