Challenge by: reminiscent-afterthought
Another instance where the dice determines our fate!
In this case, select six multichaps/collections you have in progress (either written or posted). Assign them a number from 1 to 6, and then roll the dice. Whatever number you land on, that's the fic you update. Once you've updated, roll the dice again!
If you finish a fic, you can either a) replace it with a new WIP, or b) assign that number to one of your longer works so you might get it more frequently.
Challenge is over once you've finished all six fics on your list! So if you're going for option a whenever you finish a fic, you'll be here a long while. :)
If you're the sort who'd like to split things up, you can arrange your individual lists by fandom/series, by length of chapters, by challenge, by genre etc. Lots of ways to do it. XD