Definitely can leave them a while yet and hopefully take advantage of some warmer weather to increase their size. Most of the cabbage family plants can take a licking and keep on ticking until late October in the north and well into November in the south if need be. The longer they are left within reason of course, the more sugar they accumulate and the sweeter they will taste.
If boiling or microwaving, you definitely don't want to overcook them. The cooking tips are great but there's still nothing wrong with plain old brussels sprouts with butter, salt and pepper in my book. No matter how you cook them, it's a given they're gonna stink up the house, especially the morning after.
Said, black sheep, black, do you got some wool?
Yes, I do, man, my bag is full.