For Fanfiction: Now this is a fantastic question. I used to be able to achieve this however it went. The reason the sites are never equal though are because of the follows and alerts. They? They are awesome, and I love them as a reader. As a writer too, it’s nice knowing people want to know when your latest thing is out.
Yet, when you start writing a new piece or adding more stories, guess what? They get notifications for every chapter. So if I commit to say, distributing ten new chapters everyday to different sites, then that is ten notifications being shoved into people’s mail. That’s even more annoying if it’s from stories they aren’t interested in.
Fanfiction.net I don’t mind as much. They usually just follow a story, but sometimes (and becoming more popular for me), people are granting me favorite author status. In and of itself, that is great! I have reached a real level there. However, when my Pretender fans are watching their email get filled to the brim each day with lots of things that aren’t their sauce, that gets annoying I am sure. I think AO3 has something similar. I know Wattpad does.
I used to just take hours and hours adding at least twenty five chapters to try and catch up. I have a lot of work out there. It bogs me down and then I don’t distribute, and then I will see a need to again, and there it goes all over again.
And now I have a need to again. The best way I can think to handle it is one to two chapters of work a day. This is what I did on fanfiction.net. I think it works better.
Since I don’t write new chapters of everything every day, I know that one day I will get caught up again across all sites, but it is definitely some time in the future.
For Published Fiction: This answer is so much simpler. Aggregates don’t take me everywhere. (Aggregates are the sites that distribute my work). The more I use distribution sites, the further my books can go, but I can’t get to a lot of places on my own. Also, I do experience with Kindle Unlimited every once in awhile because I like money and I might want to see if a book can do anything. So far, they haven’t done anything. I don’t foresee it much in the future, if again, but at the same time, people who like KU are getting them to try if they want. (No they aren’t. But they could.) Those two books will be out in October I think? Maybe November. Then they’ll just go wide like everything else.