I tossed some out several years ago, just threw them into an unused area at the back of the lot, & they grew but never bloomed;
this year the increases bloomed!

When a rhizome is withered (deep wrinkles) and very light, it's done all it's gonna do. Any still plump & firm have the potential for offspring.

These Iris experts say to toss them. I tossed them when I dug, trimmed and re located all of my Iris this year. I left one or two in the ground and they have yet to do anything. They are firm and look good, just a bump on the ground. I will remove and toss them this fall. G

I used to replant them when I had lots of space and very few flowers, and lots of years ahead of me. Now I don't- I don't want to wait. I want flowers in that space NOW.
I guess it depends on how much room you have, how much work you want to do, and how long you can wait.
Renee

see I never thought that they would do anything either, so i tossed them into an empty section figuring that they would do whatever it is that they'll do and i think only one didn't make new increases. i thinkthat you should put them aside somewhere and see if they do anything, but keep in mind that i didn't see any new leaves on mine until spring. also, if yours were really overgrown and are still solid, they probably will make babies as they'll be happy about the extra space, i would think...

Keep them, the worst that's gonna happen is that you'll have more irises to make you happy!