I agree, if you are done or not interested, why keep them in good reproductive health. Have fun with them. See if she'd like to try a "Tiny Nut" fetish instead like my wife has. Show her my photos so she can get an idea of what it looks like. Here is an example:
She doesn't have to put up with a hard cock down her throat, you stay limp many times even as you orgasm. And you don't have to put up with morning erections, I hated them almost as much as my useless nuts. Orgasms are less often, but much more satisfying, though. What do you think?